Higher octane than recommended a waste?

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On one hand, you have debunkers, skeptics and experts telling us using a higher octane/AKI fuel than the minimum sanctioned in the User Guide literature is of zero benefit, so don't waste your money. OTOH there are plenty of 'lay people' and 'non-experts' saying they've noticed a improvement in torque and response (and sometimes smoothness).

Naturally, certain people will simply add the latter group to the long list of "dumb people that are always falling for illusion and self-suggestion".

Given that, what do you believe and why?
 
Some turbos benefit (more power). In my opinion NA vehicles will not, unless they've developed a ping (my previous Sonata 2.4) and the higher octane makes it go away as a stop-gap until the car is checked out by a mechanic.
 
depends if the engine is tuned to take advantage of the extra octane, which most aren't.

You might see some benefit in flex-fuel cars, since they can run E85 which has a much higher octane rating.

A small number of cars, like the 98-02 Accord V6, don't even have a knock sensor at all
 
It's the placebo effect. Look it up. People think it's better, but a common layperson isn't an engineer. The BTU content of regular and super is the same. Octane is just the ability to resist knock. If their car knocked on regular, then super helps. If it didn't then it's a waste of money. Either the engine is at optimal timing or the timing is retarded. If it's at optimal timing with regular, super won't do any good.
 
Guess it depends on the vehicle. I have personally tried it in my current vehicles and it seems a waste of money. There may be a small gain in HP or fuel economy, but I couldn't tell. When I had a 1986 Mercedes, I could tell when my then girlfriend used the car and didnt put 93 in the tank. give it a try for yourself. Thats the only way you'll know. Thats what I did.
 
the truth is its somewhere in the middle.

likely there is a difference in a modern engine that only states regular but is still holding back a little, but it is going to be much smaller than claims. for example like 1 or 2% in hp and maybe 5% in torque.

in terms of optimization, holding back a little means it is optimally using the regular fuel and nothing is left on the table. it is not an optimization for the engine, it is an optimization of the fuel.

source: the lexus rx350 in 2012 was reclassified to use regular gas to boost sales even though it is exactly the same and not retuned. it was a pure marketting and sales move.
The engine power test numbers from Toyota datasheets decreased by the above percentage amounts with the only difference in fuel used.

you can lookup these same datasheets to see the difference of an engine that says regular and what it would get with premium run on what can be assumed is expert scientific procedures
 
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I believe it depends on the vehicle.

On my old car, a 2005 Chevy Cobalt with port injection and 10:1 compression, there was no difference with 93 octane.
On my new car, a 2016 Mazda3 with GDI and 13:1 compression, I get about 5% better fuel economy and possibly some improvement in engine responsiveness, though that may be in my head. The fuel economy improvement, though, is real.
 
Originally Posted By: NateDN10
I believe it depends on the vehicle.

On my old car, a 2005 Chevy Cobalt with port injection and 10:1 compression, there was no difference with 93 octane.
On my new car, a 2016 Mazda3 with GDI and 13:1 compression, I get about 5% better fuel economy and possibly some improvement in engine responsiveness, though that may be in my head. The fuel economy improvement, though, is real.

And I have tried multiple tanks in my 2016 Mazda 6 and never seen any improvement in economy.
 
Mine runs quiet on 89 octane...
87 octane and it starts pinging when I get on...
It calls for 87, strange that little bit makes a difference...
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So 89 is what it gets...
smile.gif
 
I'll let my data speak for itself.... I own 2 twin turbo DI vehicles (Ecoboost 3.5) and both "do better on premium" but require only regular.

During the fall and winter the Taurus runs great on 87. During the spring/summer it runs OK but you can tell something is off. 89 or premium and it runs great. MPG is a little better at all times on premium but not enough to offset the $0.50 or so per gallon difference in cost. All MPG records are from new. It gets 87 in winter and 89 (or premium if I'm at Costco) in the summer. 117k on it and no issues whatsoever.

At all times the F150 gets regular. Towing or not towing, summer or winter. It doesn't seem to really mind the gas as much as the Taurus. Maybe I'd see better results in the West with steeper mountains but here in the East it's fine on all gas. I've tried premium and it does get better MPG towing or not towing but it's not enough to cover the additional cost. I've got 79k on it and bought it at 48k. All MPG records from day 1 of my ownership.

There may well be more power on premium on both vehicles but I'm not paying the dyno to find out. The F150 hauls the 9-10k camper great up and down the mountains and will keep the speed limit and above with no issue, even in the dead of summer.
 
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In some cases higher octane gas has more detergents that 87. But its the detergents that may help. Some cars recommend 92 octane but will run fine on 87, so if that's the case you will notice a difference with 92. Some cars require 92 and should also use 92.

Some engines may have carbon deposits that stay hot enough to ignite gasoline during the intake stroke. Premium may help there.

Many people buy premium and subjectively think the car runs better. So be it.
 
decades ago, I had a 4Runner with the 3VZE...my first high comp (back then) Japanese motor with knock sensors. Engine had to work pretty hard to drag the 4Runner around at highways speeds.

Through diligent measurement on trips, the high octane always paid for itself in fuel savings on interstate trips...the engine could use the fuel...it's the only vehicle that I've ever had which had that marked difference. Around town could measure nothing.

The Caprice, L67, standard with 6lb boost was marked "premium recommended", but could run regular...would just detune spark and fuel poorer performance...however, fitting a 10 pound pulley, it no longer has the ability to run RUG.
 
I can actually watch the computer pull back timing on the Caprice, Silverado and Trans Am. The Trans Am requires premium.
The Caprice and Silverado do not. If you don't think tuned to run on lower octane doesn't mean "Hey pull some timing out" Get yourself HP tuners and watch it. The truck is the worst. You can see it pull a ton of timing out with 87 Octane.
With premium you most likely can't tell the difference but your car knows.

I can certainly see it when towing and the MPGs on the truck.

The Caprice not so much but I can, with HP tuners at WOT see it pull timing back on 87 octane.

I have not messed the Malibu, however it only requires 87, but tells you that best performance is achieved with premium.
 
What about the detergent factor? If you want the cleanest for your port fuel injection you have to pay for shell premium which is loaded with goodies
 
I probably should have read some of the replies before asking this question.

I realize using higher octane gasoline in an older vehicle such as one with a normally aspirated 8:1 C/R engine and no engine management system is a waste of money but if a vehicle has an engine management system on it (no vacuum advance, external control model, etc.) where the engine uses a knock sensor to adjust the timing accordingly, is there any change using higher octane fuel would allow the engine management system to advance the timing further under cruise (until a ping is detected) to give more power or fuel economy? Or is the ignition timing set by the EPA to where it won't go above a certain degree? And you would have to buy one of those "power chips" to see any benefit?

I tried an experiment with my 2003 Subaru Baja one year. I had planned on replacing the tires before winter since this is my "snow vehicle" and decided to try something.

Before heading off to the beach, I filled up with 93 octane and inflated the tires to 45 PSI (the maximum cold pressure rating). I filled up about 300 miles from home and checked my mileage. Normally I'd get about 29 or 30 mpg. This time I got a whopping 33 mph.

I doubt that gaining 3-4 MPH would justify wearing out tires and the cost of higher octane fuel. My guess is over inflating the tires improved the fuel economy but the higher octane fuel did nothing. Also I may not have hit any traffic jams.
 
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Originally Posted By: PeterPolyol
On one hand, you have debunkers, skeptics and experts telling us using a higher octane/AKI fuel than the minimum sanctioned in the User Guide literature is of zero benefit, so don't waste your money. OTOH there are plenty of 'lay people' and 'non-experts' saying they've noticed a improvement in torque and response (and sometimes smoothness).

Naturally, certain people will simply add the latter group to the long list of "dumb people that are always falling for illusion and self-suggestion".

Given that, what do you believe and why?


Depends on engine design and how it is programmed. Most of the newer turbo di engines can add timing and boost and make more power with higher octane. Some high compression NA engines can do the same thing with advancing timing.

My car is not programmed to take advantage of anything over 87 from the factory. If I buy a tune and reprogram the ECU it can make 25 more HP by messing with valve and ignition timing. It's really interesting.

So the correct answer is, it depends
 
I don't think people realize how many variables there are that can affect gas mileage. Summer gas has slightly more BTU's than winter gas. Temperature and humidity are also factors. The car makes more power in the winter with colder denser air and the a/c off. It's less power in the summer with the a/c on. With all that, the butt dyno is basically worthless. I use the same gas all the time and my gas mileage can vary from 16 to 28 depending on what kind of city traffic vs highway vs pure highway. There's no controlled data where you have repeatable, reproducible results. And all the engineering says otherwise. Yet people still believe in the marketing because they don't know any better.
 
I am running a stage 1 91 tune and put 93 octane for extra insurance. The last time I had the 93 tune and was running 93 octane, I got some feedback knock.... no thanks. Octane quality has been inconsistent for me in the nyc area
 
I used to own a 2000 Mitsubishi Montero Sport with the 3.0 V6. It would ping a bit on load so I ran premium. Now I notice that the newer 6B31 V6 recommends premium.

On a Kia Sportage forum for those running the 2.0 T-GDI engine, they have been cracking spark plugs and a suggestion both from members and from Kia is to run premium.

So it seems like a case by case thing. Most can get by with regular.
 
Octane is like rungs on a ladder. You only need to go as high as to do the job.
I've experienced 2 times when 89 was better than 87. Both were trucks, both were towing, and heat of summer with high humidity. The rest of the time, 87, like the manual recommended, was fine.

That being said, pump swill is a [censored] shoot.
There is a range of R+M/2 worked in to get to the 87, and 91 or 93 octane levels, and the only thing that companies care about meeting the minimum spec for the least amount of coin. Ethanol is 113 RON, and figures into the overall mix when it's blended in.

The Wiki Octane_rating is actually pretty good, and the Effects section describes what octane is and does.
 
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