So the wife filled up the VW with 87 octane

[umungus1122]

Originally Posted by AC1DD
Originally Posted by ammolab
So VW built the car you wanted, but they aren't able to tell you what gas it uses?

If built and tuned for 87 Octane higher octane fuel does nothing but waste money.


Wrong.

In this case the ECU can take the extra octane and advance the timing and change a few other parameters and get slightly better MPGs and performance.
It's enough to make an extra 20-25 cents a gallon worth it, anything more than that it isn't cost effective.

Even VWs made in the mid 1990s could benefit in this way.

Premium costs approximately $.40-.60 more than 87 these days. In most cases the slight increase in power one might see in factory-tune guise is not cost effective.

 

[CharBaby]

I've owned only 1 vehicle that actually allowed for a higher octane and that was a 2001 Lexus RX300. The owner's manual stated(this is not a quote)...87 octane is acceptable and 91 octane or higher is recommended for better performance. It didn't say what performance so, I would assume it was power.

Turns out(from searching) that the power increase was 2 horse power. And in the 15 years that we owned this RX300, I'd fill up with higher octane fuel for several tanks in a row, just to get some form of a baseline.

NEVER ONCE did I ever experience any feel of extra power and my fuel economy at best was the same as on 87 octane. If the fuel economy was ever better with the higher octane, it was so small of a difference that, I may have achieved the same fuel economy on 87 octane for that particular tank of gas anyway(which often happened).

At that time of ownership, if higher octane fuel(91-93 in my area) cost ~10% more than 87 octane, there was no way that I ever achieved 10% extra of anything except 10% more money out of my wallet. Today, this is more like >20% higher..."What's in your wallet?"

 

[wemay]

Originally Posted by Char Baby
I've owned only 1 vehicle that actually allowed for a higher octane and that was a 2001 Lexus RX300. The owner's manual stated(this is not a quote)...87 octane is acceptable and 91 octane or higher is recommended for better performance. It didn't say what performance so, I would assume it was power.

Turns out(from searching) that the power increase was 2 horse power. And in the 15 years that we owned this RX300, I'd fill up with higher octane fuel for several tanks in a row, just to get some form of a baseline.

NEVER ONCE did I ever experience any feel of extra power and my fuel economy at best was the same as on 87 octane. If the fuel economy was ever better with the higher octane, it was so small of a difference that, I may have achieved the same fuel economy on 87 octane for that particular tank of gas anyway(which often happened).

At that time of ownership, if higher octane fuel(91-93 in my area) cost ~10% more than 87 octane, there was no way that I ever achieved 10% extra of anything except 10% more money out of my wallet. Today, this is more like >20% higher..."What's in your wallet?"


That's the crossroads i find myself at as well. Choosing 87 unless any empirical evidence shows o should do otherwise.

 

[wemay]

Here's a copy/paste directly from the Owners Manual...

"... If Regular gasoline is recommended for your engine, you may be able to enhance engine performance by using Premium gasoline.

The recommended gasoline octane rating for your engine is listed on a label inside of the fuel filler flap. This rating may be specified according to AKI (CLC) or RON (ROZ) standards..."

And yes, 87 is what's on the inside of the filler cap door.
After ~300 miles, I've noticed zero difference. If there is/are any, it's imperceptible. But the difference between 93 and 87 in price is approximately .60/gallon.

 

[MParr]

We run 93 octane in both of our cars. We started using 93 octane when we had the 2013 KIA Optima. We took this route to prevent the Theta II engine from blowing.

 

[Snagglefoot]

No biggie, but horsepower is proportional with rpm. To extract the maximum horsepower from your car you need to redline the engine. If you are not doing that you aren't extracting the maximum amount of power. Using high octane gasoline doesn't help much ( even assuming the tune can take advantage of it) if you already are under utilizing your engine's power.

 

[Andrew1972]

Originally Posted by LotI
It's worth about 5hp, from the Fifth Gear test years ago. It lets VW advertise a wee bit higher number.

It's tuned for 93, but retards timing when used with perfectly usable 87.


The Passat/Tiguan share a detuned for economy 2.0T with Budack cycle engine that produces 184HP but a decent torque number. The GTI you have is tuned for improved HP on premium but can run with slightly reduced power on regular.

The reason the OP notices no difference is that the engine is tuned to run well on regular with a turbo engine because it was design criteria and DI helps. I have the same engine likely in our 2018 Tiguan with 55k and only once did we put in premium as regular not available. Neither wife/nor I noticed any difference in power.

 

[nickaluch]

Originally Posted by MParr
We run 93 octane in both of our cars. We started using 93 octane when we had the 2013 KIA Optima. We took this route to prevent the Theta II engine from blowing.

How is that going to help it from blowing up?

 

[Trav]

Originally Posted by Donald
There are cars that require high octane and ones that recommend it.

If its recommended then its your choice to see how it runs on 87.

If it requires it you have no choice.


+1 spot on. Gas is cheaper than pistons I say.

 

[Hall]

Originally Posted by wemay
Here's a copy/paste directly from the Owners Manual...

"... If Regular gasoline is recommended for your engine, you may be able to enhance engine performance by using Premium gasoline.

One word in that sentence jumps out at me. Know which word I'm referring to ?

Originally Posted by AC1DD
It's enough to make an extra 20-25 cents a gallon worth it, anything more than that it isn't cost effective.

20-25 cents higher ? I wish. It's more than double that here - a 60 cent differential. My Infiniti specs 87 octane by they "recommend" 91. On 87, I can honestly feel a slight impact during acceleration or other heavy throttle applications. I used 91-93 octane for a while and then tried 89 octane and noticed absolutely no difference so I've been using that for a while now.

 

[SeaJay]

Let me guess, the old idea from my father's generation (and I am a boomer!) is still going strong!.

The idea was that the higher octane gasoline must be better since it cost more and was labelled as premium, and any car that used only premium would give better and longer lasting service to its owner. Didn't matter if it was the smallest slant six in a smaller Dodge with a single barrel carb, premium gasoline was better and should be used by all who care enough about their car to give it the very, very best.

 

[wemay]

Originally Posted by hallstevenson
Originally Posted by wemay
Here's a copy/paste directly from the Owners Manual...

"... If Regular gasoline is recommended for your engine, you may be able to enhance engine performance by using Premium gasoline.

One word in that sentence jumps out at me. Know which word I'm referring to ?

Originally Posted by AC1DD
It's enough to make an extra 20-25 cents a gallon worth it, anything more than that it isn't cost effective.

20-25 cents higher ? I wish. It's more than double that here - a 60 cent differential. My Infiniti specs 87 octane by they "recommend" 91. On 87, I can honestly feel a slight impact during acceleration or other heavy throttle applications. I used 91-93 octane for a while and then tried 89 octane and noticed absolutely no difference so I've been using that for a while now.


If that's it, me too.

 

[nickaluch]

Originally Posted by tenderloin
Is Premium Gas Worth It? Car and Driver

Interesting read thanks for posting

 

[ARCOgraphite]

Originally Posted by wemay
She used my car the other day while I changed the oil on her Hyundai. Being close to "E" she decided to fill'er up. She went to the Mobil station next to our Publix grocery and filled the Passat 2.0T with 87 Octane as per the sticker on the filler door. I gotta tell, I haven't noticed an iota of difference for the 300 miles it's been driven since. Maybe 87 isn't the devil in modern turbocharged sedans calling for it.


I was mixing in some premium while my Jetta 1.4t was breaking in. Sometimes it appeared to help, othertimes it didnt
I"m on my third tank of 87 oct Irving and it doesn't seems to care.
I can notice with the 6 speed manual.

 

[dbias]

Higher octane gas is designed to be harder to ignite and this aspect slightly decreases LSPI.
Most all high octane gas has greatly increased detergents and corrosion inhibitors which helps the fuel system stay cleaner and prolong injectors health. In those vehicles designed to take advantage of it I feel its probably a good thing to use it.

 

[Trav]

Originally Posted by SeaJay
Let me guess, the old idea from my father's generation (and I am a boomer!) is still going strong!.

The idea was that the higher octane gasoline must be better since it cost more and was labelled as premium, and any car that used only premium would give better and longer lasting service to its owner. Didn't matter if it was the smallest slant six in a smaller Dodge with a single barrel carb, premium gasoline was better and should be used by all who care enough about their car to give it the very, very best.


Absolutely not, it has to do with the electronic engine controls, amount of boost pressure, spool up speed, fuel delivery system, shape of the combustion chamber, ignition and a host of other things. Low boost engines with small turbos usually mounted close to or on the head/integrated exhaust manifold with high pressure DI are nowhere near as finicky and are less effected by lower octane than a large high pressure unit that produces lots of boost commonly found in some older models and tuned engines, keeping them spooled up to minimize lag can be a bit of challenge and don't work well as daily drivers for most people.

Interesting article.

http://www.superchargersonline.com/index.php?main_page=page&id=46

.

 

[blufeb95]

Isn't the requirement of premium on turbo cars and high compression N/A engines more of a thing with port injection since the fuel air mixture is in the cylinder for the entire compression stroke whereas modern GDI engines can inject the fuel late in the compression stroke which makes pre detonation less of an issue. If the cars will run fine on 87 or 88(E15) I'd just stick with that, I don't know what it's like elsewhere but in Muncie, Indiana and the surrounding area, it's like 60 cents a gallon more for 93 over 87 at most stations, and some of the top tier places like Phillips or Shell charge like 70 or 80 cents.

 

[bachman]

I'm sure there are so many variables it's all over the board but I do recall the CX-9 (4 cyl turbo) we have as advertised with 250 hp/300 ft/lb with premium petrol. This stuff weighs heavily on my brain ... NOT !

I think of it as advertising sizzle and specs are probably amplified by in-laboratory conditions. Sunny day at sea-level with eco-tires and no wind, sun radiation, temperatures and humidity offering magical results. Mountain West gas at mid grade is my usual in both cars. Truthfully, I think more about whether to grab a mint tooth-pick or regular at the diner. Mint wont last as long though.

Many years ago, I'd read (and believed) all the fascinating engine technology and performance parameters plus, engines tuned to the petrol that was put in for optimal results or 'safe' for the motor. Computers, ECU, fuel management ? I dunno, I just have faith. There are so many techno advantages and proven results over the past decades, I still believe.

 

[Snagglefoot]

Originally Posted by tenderloin
Is Premium Gas Worth It? Car and Driver


Excellent write up. Worth the read.

 

[gathermewool]

Originally Posted by Snagglefoot
Originally Posted by tenderloin
Is Premium Gas Worth It? Car and Driver


Excellent write up. Worth the read.

Agreed, excellent read.

The only thing that I'd like to know, is whether they ran each engine hard on each respective AKI fuel to let the ECM learn prior to each test.

IIRC, my previous STI would knock the dynamic advance multiplier to around 0.6 after an ECM reset and would take a series of pulls at higher boost before creeping back up to 1.0. The fueling tables also take some time and NEED to be filled in for each cell at various RPM and loads.

I have not looked recently, but I believe my current Forester XT (DIT engine) starts with a higher DAM after an ECM reset, but I can't recall if it actually starts out at 1.0 or lower, like the STI. Regardless, its fueling tables are wiped after an ECM reset and will also need to repopulate.

//

One final thought. Each case in the article showed improvements in one area or another while using higher octane. Some of this could be noise, variation in day-to-day testing an error of the recording devices, but some of it could be due to actual changes due to the ECM sensing actual knock. The best example of this was during their testing of the F-150, where they reported not only measured differences but butt-dyno differences. They measured a lower level of boost, but I'm sure the ECM was also pulling timing AND changing fueling.

It's the latter two that concern me. It's very likely that there will be no difference, especially with vehicles that don't have any issues with carbon buildup, LSPI or fuel dilution, but what about cars that are prone to these things? Isn't the Honda 1.5L known for fuel dilution? Is this made worse using lower octane fuel?

Are we saving money now (using 87 vice 91/93 AKI) and buying ourselves into future engine problems? Probably not, but something that concerns me, nonetheless.