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#2731644 - 09/01/12 12:33 PM Unleaded in a car that`s specd for premium.
aquariuscsm Online   content


Registered: 12/30/06
Posts: 9552
Loc: South Texas,USA
My Z is specd for "Premium Unleaded Fuel Only". Last week I accidentally put regular unleaded in it (yeah,I had my head in the clouds!). What`s weird,my car seemed to run smoother and had harder pull and smoother upper rpm acceleration. Seemed to get better gas mileage too. Is premium gas a sales scam?

NOTE-I get occasional "pinging" when I shift really hard and put my foot in it,BUT,that happens whether I use premium or regular unleaded. Is this pinging being caused by the ethanol being put into gas nowadays?

I also read that using regular unleaded in a car that`s specd for premium won`t hurt a thing (Cartalk.com).

What`s everyone`s take on this?
_________________________
1996 Nissan 300ZX 5-speed,Arctic Pearl(#175 of 300)
Syntec 10W40/Fram Ultra
Amsoil MTG(tranny)
Amsoil 80W90 GL5(rear diff)
Mobil 1 ATF
Redline Water Wetter

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#2731647 - 09/01/12 12:37 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
BrownBox88 Offline


Registered: 11/16/11
Posts: 226
Loc: Florida
To me, using unleaded in a car spec'd for premium makes you press the gas pedal further down to make up for the lost performance of not using premium. I can tell a heck of a difference in my premium spec'd cars. I don't think it'll hurt though since the ecu will retard timing.
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1999 Mitsu Galant ES-V6 230k
2003 Yamaha YZF-R6 24k (R.I.P)

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#2731654 - 09/01/12 12:47 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
dparm Online   content


Registered: 04/19/10
Posts: 12473
Loc: Chicago, IL
Never trust the butt dyno.

The car has knock sensors and will do fine on regular, but I wouldn't make a habit of doing this.

Whenever my folks drive to Kanasas City (to see family), they used to run 87 in their Infiniti I30t. For highway driving there was no difference and it saved them some cash on the 1000 mile round trip.
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#2731672 - 09/01/12 01:16 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
HTSS_TR Offline


Registered: 04/17/06
Posts: 12901
Loc: Irvine, CA
I had been using regular in all my cars that specd for premium. I could not detect any difference in performance/acceleration, even in the S2000 which I redline several times a day.

Yes, it's cheaper and getting better gas mileage to boost.
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#2731680 - 09/01/12 01:27 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
EricF Offline


Registered: 07/14/09
Posts: 1557
Loc: SF Bay Area
i ran regular in my wife's old 01 eclipse (glad to have gotten rid of that money pit) and it was fine. Ran premium when I went to smog it, then back to regular. gas mileage never changed (was poor anyway) and it didn't even notice.

and yeah, the knock sensors did their job just fine!
Did this for 5 years.
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1993 Ford Ranger XLT 4.0L 4x4 (240k) 5W-30 Synpower
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#2731698 - 09/01/12 01:49 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
Pablo Offline


Registered: 10/28/02
Posts: 46594
Loc: Duvall WA - Pacific NW USA
Did it REALLY get better MPG? That would be the only difference we get with 92 vs 88 R+M/2 fuel. Slightly better mpg with 92

"Premium" should only have a bit better resistance to knock, other than that I think the premium has "more power" is a scam for sure, and premium has "better additives for cleanliness" is debatable.

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#2731704 - 09/01/12 01:59 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
gathermewool Online   content


Registered: 01/09/09
Posts: 3468
Loc: CT
I've run bad premium in my STI and it was noticeable in the logs, in form of knock. I'd trust some one like me who logs for knock and dynamic advance over any anecdotal evidence any day. Also, I'm going to point out to others the list of fluids you've got in that thing. If you wanted to skimp on any one fluid and still be safe, fuel wouldn't be much choice.

With that said, a non-turbo vehicle that requires premium because of high compression ratio and/or aggressive timing is a whole different beast, so running regular is more within the capability of the ECM to pull timing and prevent damage.

In these instances, and IMO, it's going back and forth between higher and lower octane that increases the risk of damage. In other words, if you want to run regular some of the time, you might as well run it all the time. Otherwise, you run the risk of "putting your foot into it" after just filling up with regular and the ECM having to play catchup the pull timing due to knock.

FYI: The car's ECM may aggressively combat knock by quickly pulling timing, but all it takes is one good knock event to cause damage, be it a spun bearing or the piston ringland.
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#2731707 - 09/01/12 02:01 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
Scott_Tucker Offline


Registered: 12/31/09
Posts: 840
Loc: Santa Cruz, Ca.
Premium fuel is not a scam, it can produce more power. However, there is no reason to sell three grades at the pump. It is just a marketing scam. All cars could be tuned to run on the same octane fuel. My civic is noticeably slower on 87. If you think your car is making more power on 87 either the premium you were using was bad, or you're imagining things.
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#2731713 - 09/01/12 02:06 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
Trinh Offline


Registered: 07/13/10
Posts: 46
Loc: nj, usa
Originally Posted By: aquariuscsm
My Z is specd for "Premium Unleaded Fuel Only". Last week I accidentally put regular unleaded in it (yeah,I had my head in the clouds!). What`s weird,my car seemed to run smoother and had harder pull and smoother upper rpm acceleration. Seemed to get better gas mileage too. Is premium gas a sales scam?

NOTE-I get occasional "pinging" when I shift really hard and put my foot in it,BUT,that happens whether I use premium or regular unleaded. Is this pinging being caused by the ethanol being put into gas nowadays?

I also read that using regular unleaded in a car that`s specd for premium won`t hurt a thing (Cartalk.com).

What`s everyone`s take on this?

i also have a highly modified 300zx putting down about 500rwhp, do you have a na or a tt?


Edited by Trinh (09/01/12 02:07 PM)

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#2731717 - 09/01/12 02:10 PM Re: Unleaded in a car that`s specd for premium. [Re: Pablo]
Trinh Offline


Registered: 07/13/10
Posts: 46
Loc: nj, usa
Originally Posted By: Pablo

"Premium" should only have a bit better resistance to knock,

in forced-induction applications, they have superior resistance to knock.

i know someone who was trying to save some money by running regular in a turbo-ed nissan, and his pistons cracked due to knock.

Originally Posted By: Scott_Tucker
It is just a marketing scam. All cars could be tuned to run on the same octane fuel.

it's not a marketing scam, higher octane is better at suppressing knock, why do you think the big horsepower guys run race fuel, C16 or Q16, etc.? the newest fad, for lack of a better word, is E85. again, this is for forced inductions, if you have a naturally-aspirated platform, you don't really see the benefits.


Edited by Trinh (09/01/12 02:14 PM)

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#2731729 - 09/01/12 02:19 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
Trajan Offline


Registered: 07/16/05
Posts: 3314
Loc: SE PA
I did the same thing in the Z4, though on purpose. Less power, less mpg.

Though if the knock sensors died....
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#2731731 - 09/01/12 02:21 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
tommygunn Offline


Registered: 01/27/11
Posts: 2534
Loc: usa
Premium fuel is for higher compression engines and when you're running boost. Regular in a car running either means the ECU has to cripple things a little and retard timing and reduce boost but it should run fine, but I would be wary of potential engine damage as the car will keep trying to push timing and boost up for high octane fuel.

Premium fuel in a car calling for regular fuel is flatout stupid.

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#2731736 - 09/01/12 02:24 PM Re: Unleaded in a car that`s specd for premium. [Re: Trinh]
aquariuscsm Online   content


Registered: 12/30/06
Posts: 9552
Loc: South Texas,USA
Originally Posted By: Trinh
do you have a na or a tt?


I have a completely stock n/a. ONLY mod I`ve ever done was the bronze SPL shifter bushings. Tried a short shifter once,hated it,and went back to the stock shifter.
_________________________
1996 Nissan 300ZX 5-speed,Arctic Pearl(#175 of 300)
Syntec 10W40/Fram Ultra
Amsoil MTG(tranny)
Amsoil 80W90 GL5(rear diff)
Mobil 1 ATF
Redline Water Wetter

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#2731742 - 09/01/12 02:30 PM Re: Unleaded in a car that`s specd for premium. [Re: Trinh]
aquariuscsm Online   content


Registered: 12/30/06
Posts: 9552
Loc: South Texas,USA
Originally Posted By: Trinh
it's not a marketing scam, higher octane is better at suppressing knock, why do you think the big horsepower guys run race fuel, C16 or Q16, etc.? the newest fad, for lack of a better word, is E85. again, this is for forced inductions, if you have a naturally-aspirated platform, you don't really see the benefits.

Now I know legit race gas is definitely not a scam,but I really do have to wonder about your typical gas stations. The world is full of marketing scams and ploys to get more of the consumer`s money. So who knows,huh!

Now my car NEVER knocks,it just will ping when I shift hard with my foot in it. Sounds like a very *tinny* tapping sound from the valvetrain. BUT,it does this on premium too,regardless of the brand of gas.

Is it the ethanol causing the pinging? Mr car NEVER pinged before that [censored] ethanol gas came on the market.
_________________________
1996 Nissan 300ZX 5-speed,Arctic Pearl(#175 of 300)
Syntec 10W40/Fram Ultra
Amsoil MTG(tranny)
Amsoil 80W90 GL5(rear diff)
Mobil 1 ATF
Redline Water Wetter

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#2731775 - 09/01/12 03:03 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
Trinh Offline


Registered: 07/13/10
Posts: 46
Loc: nj, usa
Originally Posted By: aquariuscsm

Now my car NEVER knocks,it just will ping when I shift hard with my foot in it. Sounds like a very *tinny* tapping sound from the valvetrain. BUT,it does this on premium too,regardless of the brand of gas.

Is it the ethanol causing the pinging? Mr car NEVER pinged before that [censored] ethanol gas came on the market.

i thought E10 has been around for a really long time?
i don't even remember the last time i got gasoline that had no ethanol in it? laugh

have you checked to see if it's perhaps lifter tick or vtc tick? both common noises in our cars.

let's hope it's not rod knock.

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#2731778 - 09/01/12 03:08 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
aquariuscsm Online   content


Registered: 12/30/06
Posts: 9552
Loc: South Texas,USA
Nah,it`s just that light metallic pinging sound when I push it really hard between shifts. My Z only has 78,000 miles on it and I usually drive it like a lil old man. I only get the pinging on a fully warmed engine on 100F+ degree days. I`m just thinking it`s today`s [censored] ethanol blend gas. My Z31 did it,and my Olds w/3800 did it if I used really cheapy gas in it. Yeah,I`m thinking ethanol hasn`t really been common for a long time,but then again,I`m 43 years old haha.

But no,never have had lifter tick. She purrs like a happy kitten :^)


Edited by aquariuscsm (09/01/12 03:12 PM)
_________________________
1996 Nissan 300ZX 5-speed,Arctic Pearl(#175 of 300)
Syntec 10W40/Fram Ultra
Amsoil MTG(tranny)
Amsoil 80W90 GL5(rear diff)
Mobil 1 ATF
Redline Water Wetter

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#2731800 - 09/01/12 03:41 PM Re: Unleaded in a car that`s specd for premium. [Re: Trinh]
Scott_Tucker Offline


Registered: 12/31/09
Posts: 840
Loc: Santa Cruz, Ca.
Originally Posted By: Trinh
Originally Posted By: Scott_Tucker
It is just a marketing scam. All cars could be tuned to run on the same octane fuel.

it's not a marketing scam, higher octane is better at suppressing knock, why do you think the big horsepower guys run race fuel, C16 or Q16, etc.? the newest fad, for lack of a better word, is E85. again, this is for forced inductions, if you have a naturally-aspirated platform, you don't really see the benefits.

I'm not saying that high octane fuel is a scam, I'm saying we don't need three grades. A car that will run on 87 will run just as well on 91. The cost of producing 91 isn't much different than producing 87 as it would seem by the price, so the extra cost of having additional machinery and having to ship it separately seems like it would even out. Of course, people want to feel like they have a choice so I can understand why they do it like that.
_________________________
2012 Honda Civic Si, Dyno Blue Pearl

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#2731883 - 09/01/12 05:44 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
Garak Online   content


Registered: 12/05/09
Posts: 11155
Loc: Regina, Saskatchewan, Canada
I've only had a problem with premium (used in vehicles speced for it) a couple times. One was simply a bad batch in the old Audi, and it ran terribly for the whole tank. Such is life.

The other time was years ago, and that's getting premium at a place that hardly moved any. It was probably stale, or at least degraded. Perhaps that's what you encountered.
_________________________
Plain, simple Garak.

2008 Infiniti G37 coupe - Mobil Delvac 1 ESP 5w-40, Hastings LF113
1984 F-150 4.9L six - Quaker State GB 10w-30, Wix 51515

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#2731895 - 09/01/12 05:54 PM Re: Unleaded in a car that`s specd for premium. [Re: Scott_Tucker]
Trinh Offline


Registered: 07/13/10
Posts: 46
Loc: nj, usa
Originally Posted By: Scott_Tucker

A car that will run on 87 will run just as well on 91.

but the reverse is not true, a car that runs on 93-octane won't run just as well on non-premium fuel.

it's not about choice, for forced-induction or high-compression engines/cars, you NEED premium fuel.

Originally Posted By: Scott_Tucker
All cars could be tuned to run on the same octane fuel.

no, they can't, again no offense intended but a civic isn't a performance car, you can't use your car as some sort of benchmark.

for boosted and higher-compression cars, you need premium fuel.

higher-octane fuel is better at suppressing knock, you can't get around that.


Edited by Trinh (09/01/12 05:57 PM)

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#2731900 - 09/01/12 06:06 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
aquariuscsm Online   content


Registered: 12/30/06
Posts: 9552
Loc: South Texas,USA
BUT,does ethanol cause pinging? The noise I`m talking about isn`t knock. It`s a VERY faint *tinny* sounding pinging that lasts only for a millisecond if I lay my foot into it between shifts.
_________________________
1996 Nissan 300ZX 5-speed,Arctic Pearl(#175 of 300)
Syntec 10W40/Fram Ultra
Amsoil MTG(tranny)
Amsoil 80W90 GL5(rear diff)
Mobil 1 ATF
Redline Water Wetter

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#2731922 - 09/01/12 06:46 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
hemitom Online   content


Registered: 03/12/07
Posts: 740
Loc: canada
How do we really know what these gas stations are dumping in the tanks. My father told me of a gas station he knew of in the 60's that would dump some diesel in with the gas. mind you back then i,m sure the cars would not notice as long as they wouldn't over do it with the diesel fuel. I guess my point is how do you really know if there not putting regular gas in all the tanks. Does anyone ever check up on gas stations to regulate the quality of the fuel.????????
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2006 kia spectra
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#2731949 - 09/01/12 07:30 PM Re: Unleaded in a car that`s specd for premium. [Re: hemitom]
yonyon Offline


Registered: 03/06/12
Posts: 3492
Loc: NJ, USA
Originally Posted By: hemitom
How do we really know what these gas stations are dumping in the tanks. My father told me of a gas station he knew of in the 60's that would dump some diesel in with the gas. mind you back then i,m sure the cars would not notice as long as they wouldn't over do it with the diesel fuel. I guess my point is how do you really know if there not putting regular gas in all the tanks. Does anyone ever check up on gas stations to regulate the quality of the fuel.????????


It isn't even just the station that does that sort of thing, at least that's how it is here. Weights and measures comes around (I think it's once a year?) to measure the volume from the dispensers in every grade of gasoline and diesel fuel. It all goes back into the regular tank.

The gasoline has to go somewhere and it's legal to put higher octane stuff in the lower octane tank. The diesel they could spill out on the ground if they could be sure it didn't get contaminated with gasoline, but it's easier to just dump that in with the regular which is still legal.

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#2731972 - 09/01/12 07:51 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
Garak Online   content


Registered: 12/05/09
Posts: 11155
Loc: Regina, Saskatchewan, Canada
Originally Posted By: aquariuscsm
BUT,does ethanol cause pinging?


In my experience at least, no. I've tried ethanol premium (which is rare here, but used to me more common) and pure premium, without any noticeable operating difference.

The only pinging I've noticed since the 1970s was on one of the last Caprices where drivers were putting in real bad gas (pure gas at that station at that time). It took a couple tanks of premium to sort everything out. The sound and circumstances surrounding it were similar to what you described.

When the Audi had the bad load of premium, it just ran bad, probably retarding the timing on its own. The other bad premium experienced (a low traffic station, as per my previous post) just kept setting of a CEL until better gas was put in; it was probably retarding the timing, too.
_________________________
Plain, simple Garak.

2008 Infiniti G37 coupe - Mobil Delvac 1 ESP 5w-40, Hastings LF113
1984 F-150 4.9L six - Quaker State GB 10w-30, Wix 51515

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#2731973 - 09/01/12 07:51 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
mechtech2 Offline


Registered: 09/05/06
Posts: 19479
Loc: Chicago Area
Being unleaded or not, and being regular or premium, are two totally separate things. So the OPs queston is invalid.

If a car does indeed spec premium, it needs it for best economy and performance. No mfr would EVER spec premium if if did not need it.

That said, always use as low octane as is needed. Butt dynos and hearing for knock are not always good indicators for octane requirements.

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#2731976 - 09/01/12 07:56 PM Re: Unleaded in a car that`s specd for premium. [Re: mechtech2]
Trajan Offline


Registered: 07/16/05
Posts: 3314
Loc: SE PA
Originally Posted By: mechtech2
Being unleaded or not, and being regular or premium, are two totally separate things. So the OPs queston is invalid.

If a car does indeed spec premium, it needs it for best economy and performance. No mfr would EVER spec premium if if did not need it.

That said, always use as low octane as is needed. Butt dynos and hearing for knock are not always good indicators for octane requirements.

This!!
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#2732001 - 09/01/12 08:14 PM Re: Unleaded in a car that`s specd for premium. [Re: mechtech2]
Garak Online   content


Registered: 12/05/09
Posts: 11155
Loc: Regina, Saskatchewan, Canada
Originally Posted By: mechtech2
Butt dynos and hearing for knock are not always good indicators for octane requirements.


Absolutely. Obviously, when the taxi pinged from bad fuel, that certainly didn't mean that a 1990s era Caprice with a stock 305 needed premium. Sometimes an anomaly is just that.
_________________________
Plain, simple Garak.

2008 Infiniti G37 coupe - Mobil Delvac 1 ESP 5w-40, Hastings LF113
1984 F-150 4.9L six - Quaker State GB 10w-30, Wix 51515

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#2732091 - 09/01/12 09:10 PM Re: Unleaded in a car that`s specd for premium. [Re: EricF]
Spazdog Offline


Registered: 09/06/10
Posts: 5492
Loc: Arlington
Originally Posted By: EricF
i ran regular in my wife's old 01 eclipse (glad to have gotten rid of that money pit) and it was fine. Ran premium when I went to smog it, then back to regular. gas mileage never changed (was poor anyway) and it didn't even notice.

and yeah, the knock sensors did their job just fine!
Did this for 5 years.


The wife's former car was a 6G72 SOHC 2001 Eclipse GT. It would run fine on 87 octane in spite of the warning that it required premium.

The wife's current car is a Turbocharged PT Cruiser GT. Don't even think of using less than 93 octane. It knocks and pings badly under boost with 89. Around town with little throttle you do not notice, but when you get the turbo spooled up you definitely notice it.
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#2732104 - 09/01/12 09:21 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
PhillyJoe Offline


Registered: 03/19/09
Posts: 515
Loc: PA
My Grand Prix has a supercharger and the manual "recommends" premium which I have run since day one. No problem with paying a little extra, but sometimes the difference is 40 or 50 cents a gallon. That's a problem.

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#2732130 - 09/01/12 09:59 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
gathermewool Online   content


Registered: 01/09/09
Posts: 3468
Loc: CT
When I see knock in my logs there is ZERO audible indication of it. If you're hearing pinging while getting on it after putting the wrong grade, then you should really stop getting on it. I don't know what those blocks are made of, but I hope for your sake there are no weak links that you're severely testing...

As far as pump gas premium being questionable, I'm telling you, again, that it's all in the logs. When I get some iffy fuel it shows in my logs. As soon as a I get some fresh gas, all is well. Normally, if I see any more than a very minimal amount of knock in my logs I'll flash a 91 octane map, which also drops the knock down to zero.

I'd run the 91 octane map with 93 octane fuel all the time for added conservitism, but the 93 octane map is already conservitism, and the difference in power is very noticeable.
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#2732155 - 09/01/12 10:25 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
aquariuscsm Online   content


Registered: 12/30/06
Posts: 9552
Loc: South Texas,USA
My Z`s engine has an iron block. I DID notice that with Kroger gas,it pinged the worst. HEB and Shell gas always runs great! Walmart gas always burns up really fast and doesn`t last. Weird,huh!


Edited by aquariuscsm (09/01/12 10:27 PM)
_________________________
1996 Nissan 300ZX 5-speed,Arctic Pearl(#175 of 300)
Syntec 10W40/Fram Ultra
Amsoil MTG(tranny)
Amsoil 80W90 GL5(rear diff)
Mobil 1 ATF
Redline Water Wetter

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#2732248 - 09/02/12 01:29 AM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
SS1970chrysler Offline


Registered: 05/01/11
Posts: 1309
Loc: PA
My '62 Buick was intended for 93 and higher octane fuel, but it will run fine on 89 and higher. With 87, it will not shut off properly and will be finicky at startups.
In my case, Buick did sell a lower compression version of the same engine for use with "economy fuels", but that's not what I have. wink
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#2732306 - 09/02/12 06:18 AM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
SteveSRT8 Offline


Registered: 10/10/08
Posts: 14525
Loc: Sunny Florida
OMG, I remember 'dieseling' in my carbureted cars! Only one left here now, so the problem is gone.

I was actually disturbed by the way my first fuel injected car turned off. So sudden and final. Fuel cut off is a wonderful thing.

But back on topic, most folks do not even understand octane. Slower burning/harder to ignite fuel is not always the best fuel. I used to retune vehicles a lot in the 80's to run well on regular, and many times a bit of fuel enrichment was all they needed. Most times we ADDED timing.

Talking about tuning across differing platforms can confuse folks, as even the same cars can require slightly different tweaks to run sharp.
_________________________
"In a democracy, dissent is an act of faith."
J. William Fulbright
Best ET-12.79 @ 111 mph
4340 pounds, Street tires
Just like we go to Publix

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#2732402 - 09/02/12 08:47 AM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
Vikas Offline


Registered: 07/22/05
Posts: 8042
Loc: NorthEast
Question to OP:- When you compared regular against premiums, was it at the same gas station? OR did you use different brand of fuel?

Talking about premium, the new Acura TL just purchased has "premium required" in the owner's manual. It specifically states that anything else will cause engine damage. Being a Honda, I would have expected "premium recommended" but that is not the case.

In the past, I have routinely used regular on the cars which had "premium recommended". I did not notice any significant drop in the performance to warrant premium. SHO, Turbo Eclipse and Maxima all had been fed regular and had enough street performance and never heard any engine pinging.

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#2732461 - 09/02/12 10:12 AM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
asiancivicmaniac Offline


Registered: 01/12/05
Posts: 4035
Loc: FL
I normally run premium in my car because it's "recommended" (more like required). A couple weeks ago, I put in 87 because I was almost out of gas and the station I ended up at had the price jacked up 20¢. It ran that tank fine. Then I put in regular again because the first tank seemed fine. This tank doesn't seem to be going so well. The engine feels like it's been neutered. I can't wait to finish this tank.

And in the past, I would usually get a .5-1 mpg difference between 87 and 93 so it doesn't really cost all that much more. So back to 93 I go.

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#2732480 - 09/02/12 10:37 AM Re: Unleaded in a car that`s specd for premium. [Re: SteveSRT8]
gathermewool Online   content


Registered: 01/09/09
Posts: 3468
Loc: CT
Originally Posted By: SteveSRT8


But back on topic, most folks do not even understand octane. Slower burning/harder to ignite fuel is not always the best fuel. I used to retune vehicles a lot in the 80's to run well on regular, and many times a bit of fuel enrichment was all they needed. Most times we ADDED timing.

Talking about tuning across differing platforms can confuse folks, as even the same cars can require slightly different tweaks to run sharp.


Absolutely, but we're not talking about tuning here. We're talking about stock blocks that either recommend or require higher octane fuel.

While tuning, both fueling and timing (and valve control and wastegate duty cycle, and etc) need to be adjusted. The first thing most do in turbo Subie tunes is mess with the fueling - stock likes to keep AFR near or just less than stoich even after the onset of boost. Aftermarket or pro-tunes dump it down to ~11-12 quickly and keep it there. Tip-in enrichment is important, too, to combat exactly what the OP seems to be experiencing. Add a little more fuel and maybe take away some timing and no more pinging.

Outside of tuning for fuel, a fuel suited to your stock requirements, even if only recommended, is what should (not shall) be done (I.e., running 93 octane in an engine that recommends 91 octane is a waste of money if 91 is recommended; however, 93 is just fine if 91 is required, and the stock tune is known to be aggressive - my STI, for example.)

In the end, use what's required or recommended. You're doing yourself ZERO favors by using a lower-than-recommended octane. Unless you've got an old iron block, like the OP, or a motor known for taking abuse and low octane without spinning a bearing or damaging pistons, then run the required octane. Even if you drive gently and mostly highway, where the higher octane may provide no benefit, the first time you get on it, which we all do, damage may occur. It's as simple as that.
_________________________
14 Forester XT
Rotella T6 + Subie blue filter
08 Civic LX (Auto)
VWB 5W-20 + Fram Ultra Guard filter

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#2732613 - 09/02/12 01:01 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
aquariuscsm Online   content


Registered: 12/30/06
Posts: 9552
Loc: South Texas,USA
I`m curious,what damage can possibly occur using a lower than recommended/required gas? What components could suffer,and how?
_________________________
1996 Nissan 300ZX 5-speed,Arctic Pearl(#175 of 300)
Syntec 10W40/Fram Ultra
Amsoil MTG(tranny)
Amsoil 80W90 GL5(rear diff)
Mobil 1 ATF
Redline Water Wetter

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#2732620 - 09/02/12 01:07 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
yonyon Offline


Registered: 03/06/12
Posts: 3492
Loc: NJ, USA
Pistons, rods, anything that rods punch holes through, wristpins and rod bearings, and exhaust valves all come to mind as potentially being harmed. Nothing major, really.

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#2732644 - 09/02/12 01:20 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
aquariuscsm Online   content


Registered: 12/30/06
Posts: 9552
Loc: South Texas,USA
What exactly does higher/lower octane *do* per se? What does a higher octane gas do that a lower one doesn`t and vise versa?
_________________________
1996 Nissan 300ZX 5-speed,Arctic Pearl(#175 of 300)
Syntec 10W40/Fram Ultra
Amsoil MTG(tranny)
Amsoil 80W90 GL5(rear diff)
Mobil 1 ATF
Redline Water Wetter

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#2732682 - 09/02/12 02:02 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
Trajan Offline


Registered: 07/16/05
Posts: 3314
Loc: SE PA

http://forum.ih8mud.com/80-series-tech/160442-high-octane-fuel-vs-low-octane-fuel-facts-myths.html

http://www.state.mn.us/mn/externalDocs/Commerce/Gasoline_Octane_Facts_102902052227_OctaneFacts.pdf

http://www.ftc.gov/bcp/conline/pubs/autos/octane.shtm

http://science.howstuffworks.com/gasoline3.htm



Octane Facts
• Knock occurs when cylinder pressures are high. It is normal for an engine to ping a little at full throttle
because cylinder pressures are very high at full throttle. Engine knock, however, should not be ignored
since it can result in serious damage to the engine.

• High octane gasoline burns slower than low octane gasoline. The slow burn prevents engine knock when
cylinder pressures are high.

• If your engine runs well and does not knock or ping on low octane gasoline, there is no advantage in
switching to higher octane gasoline.

• If your engine knocks or pings, it does not necessarily mean something is wrong with the gasoline. It could
be a problem with the engine’s electronic control systems, ignition timing or exhaust gas recirculation. On a
high mileage engine, a carbon build-up in the cylinders can increase cylinder pressures and cause knock.

• Almost all of today’s new cars have fuel-injected engines that need to use gasoline with a detergent additive.
They do not necessarily need high octane gasoline with a detergent additive. Generally, new automobiles
need high octane gasoline only if the manufacturer recommends it.

• Always follow the auto manufacturer’s octane recommendations in your owner’s manual.


Edited by Trajan (09/02/12 02:02 PM)
_________________________

Lack of harm does not mean proof of benefit.

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#2732699 - 09/02/12 02:29 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
aquariuscsm Online   content


Registered: 12/30/06
Posts: 9552
Loc: South Texas,USA
*It is normal for an engine to ping a little at full throttle*

^^This. That`s what happens to me,whether it`s premium unleaded or regular unleaded. Just light pinging,no knocking whatsoever.
_________________________
1996 Nissan 300ZX 5-speed,Arctic Pearl(#175 of 300)
Syntec 10W40/Fram Ultra
Amsoil MTG(tranny)
Amsoil 80W90 GL5(rear diff)
Mobil 1 ATF
Redline Water Wetter

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#2732769 - 09/02/12 04:33 PM Re: Unleaded in a car that`s specd for premium. [Re: Trajan]
BearZDefect Offline


Registered: 08/15/05
Posts: 1890
Loc: Lexington, KY
Quote:
• High octane gasoline burns slower than low octane gasoline. The slow burn prevents engine knock when
cylinder pressures are high.

I thought high octane gasoline resists pre-ignition better than low octane, not that it burns slower once ignited.

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#2732779 - 09/02/12 04:45 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
Trajan Offline


Registered: 07/16/05
Posts: 3314
Loc: SE PA
I think that's what they mean by "burn slower."
_________________________

Lack of harm does not mean proof of benefit.

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#2732851 - 09/02/12 06:33 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
yonyon Offline


Registered: 03/06/12
Posts: 3492
Loc: NJ, USA
"Burn slower" always meant that the flame front would move more slowly to me. Igniting later wouldn't be burning slower, just burning later.

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#2732967 - 09/02/12 09:04 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
Errtt Offline


Registered: 11/14/10
Posts: 2117
Loc: California
Like a softer flame kernel - not higher flash/ignite point.

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#2733150 - 09/03/12 05:19 AM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
SteveSRT8 Offline


Registered: 10/10/08
Posts: 14525
Loc: Sunny Florida
Originally Posted By: aquariuscsm
*It is normal for an engine to ping a little at full throttle*

^^This. That`s what happens to me,whether it`s premium unleaded or regular unleaded. Just light pinging,no knocking whatsoever.


This is more advice that is HIGHLY platform specific.

Many modern cars have the top ring positioned very high up on the piston for emissions reasons. This combined with cast pistons can create a weak spot and it is VERY susceptible to ping damage.

I have personally disassembled many engines with severe damage caused by preignition. Most notable was a 78 Pontiac 400 with every single top piston ring in at least 6 pieces and a broken main bearing web in the block! This motor still ran!

Just note that some engines are designed to run at the edge of allowable timing and thus can ping a bit under certain conditions.

For others it can mean rapid death.
_________________________
"In a democracy, dissent is an act of faith."
J. William Fulbright
Best ET-12.79 @ 111 mph
4340 pounds, Street tires
Just like we go to Publix

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#2733504 - 09/03/12 01:06 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
aquariuscsm Online   content


Registered: 12/30/06
Posts: 9552
Loc: South Texas,USA
I knew a guy who had a 94 TT Z32 (was actually the service manager at the Nissan dealership) and always used regular unleaded,never used premium. Last time I saw him he had a little over 350,000 miles on it!
_________________________
1996 Nissan 300ZX 5-speed,Arctic Pearl(#175 of 300)
Syntec 10W40/Fram Ultra
Amsoil MTG(tranny)
Amsoil 80W90 GL5(rear diff)
Mobil 1 ATF
Redline Water Wetter

Top
#2739179 - 09/09/12 09:20 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
Durango Offline


Registered: 02/15/07
Posts: 2036
Loc: Los Angeles, California
Originally Posted By: aquariuscsm
My Z is specd for "Premium Unleaded Fuel Only". Last week I accidentally put regular unleaded in it (yeah,I had my head in the clouds!). What`s weird,my car seemed to run smoother and had harder pull and smoother upper rpm acceleration. Seemed to get better gas mileage too. Is premium gas a sales scam?

NOTE-I get occasional "pinging" when I shift really hard and put my foot in it,BUT,that happens whether I use premium or regular unleaded. Is this pinging being caused by the ethanol being put into gas nowadays?

I also read that using regular unleaded in a car that`s specd for premium won`t hurt a thing (Cartalk.com).

What`s everyone`s take on this?


aquariuscsm,

My Impala SS is also speced for premium as well. I was told regular can be used but expect different performance habits. Why not just use midgrade instead of regular? Either case your on board computer will make changes on your behalf.

Durango

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#2741239 - 09/11/12 10:17 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
FrankieFX Offline


Registered: 09/11/12
Posts: 8
Loc: Ontario
I actually have 350Z finding I was getting hugely inconsistent performance. My hypothesis is premium fuel sits way too long from the very low demand and is getting contaminated with water or oxidizing.

I'm an engine designer and at the point where I'm going to buy an octane meter. Ridicules. I've consulted with oil and mining companies and they use a product called fuelflux, and the company is called lubriflux. I apparently aligns fuel molecules and one of the characteristics is increase in natural octane. I bought some from their site and my 350z runs like its angry now.

If your engine is designed to run with octane, take advantage of it. Otherwise your building heat and wearing things out fsater.
_________________________
Nissan 350Z - Red Line 5w30
Chevy z24 - Valvoline high mileage 5w30
Puch maxi moped Lubriflux 2charge 2-cycle

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#2741243 - 09/11/12 10:24 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
Scott_Tucker Offline


Registered: 12/31/09
Posts: 840
Loc: Santa Cruz, Ca.
What is an octane meter?
_________________________
2012 Honda Civic Si, Dyno Blue Pearl

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#2741590 - 09/12/12 10:41 AM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
Vikas Offline


Registered: 07/22/05
Posts: 8042
Loc: NorthEast
OK, we have a got somebody who just registered here and touting a product "which aligns fuel molecules".

You should know the rest!

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#2741800 - 09/12/12 02:07 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
Eddie Offline


Registered: 12/07/03
Posts: 6648
Loc: Florida, Cape Coral
To many personal opinions and little data here. :-))
_________________________
CX5 Touring 2.5L :-)

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#2742541 - 09/13/12 10:43 AM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
2KBMW Offline


Registered: 10/29/03
Posts: 461
Loc: Ontario Canada
Originally Posted By: aquariuscsm
My Z is specd for "Premium Unleaded Fuel Only". Last week I accidentally put regular unleaded in it (yeah,I had my head in the clouds!). What`s weird,my car seemed to run smoother and had harder pull and smoother upper rpm acceleration. Seemed to get better gas mileage too. Is premium gas a sales scam?

NOTE-I get occasional "pinging" when I shift really hard and put my foot in it,BUT,that happens whether I use premium or regular unleaded. Is this pinging being caused by the ethanol being put into gas nowadays?

I also read that using regular unleaded in a car that`s specd for premium won`t hurt a thing (Cartalk.com).

What`s everyone`s take on this?


Don't worry. I've been using mid grade (89) in my BMW
for over two years . No problem and no difference in performance that I can tell.

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#2742604 - 09/13/12 11:56 AM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
cutter Offline


Registered: 02/06/12
Posts: 759
Loc: Philadelphia, PA
I stopped at the Farley S rest stop on the AC expressway for a full fill up. It's a Sunoco there. When I asked for "Ultra" 93, the gas attendant did a double take and asked again if I wanted Ultra. She said she had not heard anyone ask for anything but regular. I'm not sure how long she had been working, but even if she had just started, it makes me wonder how long premium sits underground.

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#2742735 - 09/13/12 03:03 PM Re: Unleaded in a car that`s specd for premium. [Re: gathermewool]
webfors Offline


Registered: 06/06/06
Posts: 3618
Loc: Ottawa
Originally Posted By: gathermewool
Originally Posted By: SteveSRT8


But back on topic, most folks do not even understand octane. Slower burning/harder to ignite fuel is not always the best fuel. I used to retune vehicles a lot in the 80's to run well on regular, and many times a bit of fuel enrichment was all they needed. Most times we ADDED timing.

Talking about tuning across differing platforms can confuse folks, as even the same cars can require slightly different tweaks to run sharp.


Absolutely, but we're not talking about tuning here. We're talking about stock blocks that either recommend or require higher octane fuel.

While tuning, both fueling and timing (and valve control and wastegate duty cycle, and etc) need to be adjusted. The first thing most do in turbo Subie tunes is mess with the fueling - stock likes to keep AFR near or just less than stoich even after the onset of boost. Aftermarket or pro-tunes dump it down to ~11-12 quickly and keep it there. Tip-in enrichment is important, too, to combat exactly what the OP seems to be experiencing. Add a little more fuel and maybe take away some timing and no more pinging.

Outside of tuning for fuel, a fuel suited to your stock requirements, even if only recommended, is what should (not shall) be done (I.e., running 93 octane in an engine that recommends 91 octane is a waste of money if 91 is recommended; however, 93 is just fine if 91 is required, and the stock tune is known to be aggressive - my STI, for example.)

In the end, use what's required or recommended. You're doing yourself ZERO favors by using a lower-than-recommended octane. Unless you've got an old iron block, like the OP, or a motor known for taking abuse and low octane without spinning a bearing or damaging pistons, then run the required octane. Even if you drive gently and mostly highway, where the higher octane may provide no benefit, the first time you get on it, which we all do, damage may occur. It's as simple as that.


^ This. Everything else is falsehoods grin
_________________________
08 Forester 5mt, Edge 10w30, XG7317
13 Dodge GC, VWB 5w20/10w30 mix, PClassic OF
13 Suzuki SFV650, OEM 10w40, OEM OF
All small engines; RT5 10w30

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#2742786 - 09/13/12 03:49 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
mechtech2 Offline


Registered: 09/05/06
Posts: 19479
Loc: Chicago Area
And like I said, no mfr would spec a higher and more expensive octane for no reason.
They would always prefer [for a bunch of reasons] to spec the lowest octane.
But they don't.
Why?
Because the extra octane is needed. Maybe sometimes for certain conditions, but it IS needed.

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#2743014 - 09/13/12 08:36 PM Re: Unleaded in a car that`s specd for premium. [Re: aquariuscsm]
tommygunn Offline


Registered: 01/27/11
Posts: 2534
Loc: usa
Yeah, I certainly wouldn't drive a turbo'ed car on regular gas an expect to get anything but alot of timing pulled along with boost to compensate...and therefore less performance.

Theoretically you can but if you're doing that why the [censored] did you buy a turbo sportscar in the first place?

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