Switching to Premium gasoline

[TiGeo]

Turbo = HEAT = Premium

= the only way to know if there is a benefit is to log it.

 

[TiGeo]

I got a 2024 Audi A4 Quattro four-door sedan four-cylinder with turbo and it recommends high octane/premium gasoline. It will destroy the motor if you don’t run this.

Destroy is a bit much. It won't run optimally or with as much power but the ECU should be able to retard the timing enough to manage a stray tank of 87...there would be a whole lot of destroyed engines if not. I've run 87 in an modern Audi rental with the same engine...zero issue driving normally.

 

[Astro14]

= the only way to know if there is a benefit is to log it.

Benefit in street driving?

I’m curious what you use in your modified track cars. I would assume given the turbo chargers, and the output potential of the engine, but you use some form of race gas.

Like Sunoco 260, perhaps?

 

[Mechanician]

The one way to know for sure is to have a scan tool hooked up while you’re driving and see if the computer is pulling any timing out while using 87 octane. If it’s not, then the use of anything higher is just wasted money.
With some of my high performance cars I was finding that timing was getting pulled out when I ran 91 octane and no timing was pulled with 94. In my Corvette I can actually hear mild pinging at part throttle (and around 1500-2000 rpm) if I use 91 octane but it goes away with 93-94. The manual recommends 93 (but strangely enough, the earlier C7s recommended 91 even though the engines are identical in every way)

^this^
The mixture isn't what's adjusted for octane. The oxygen sensor would not like that.
Typically there are different timing "maps" programmed for the different octanes, on vehicles that recommend premium.
The performance, and MPG gains happen due to the ignition timing being adjusted.
EGR is also used to lessen knock some times - that's not going to help performance either.

 

[TiGeo]

Benefit in street driving?

I’m curious what you use in your modified track cars. I would assume given the turbo chargers, and the output potential of the engine, but you use some form of race gas.

Like Sunoco 260, perhaps?

Yes as in logging street driving and seeing if you have knock sensor feedback. Then running premium and seeing if it stops. If so you are making more power but the impact for street driving will be low becuase that power is typically on suppression.

I run pump 93 in my Sportwagen because that's what the tune is for. Aftermarket tuning is quite different than factory and the "octane cushion" isn't there like on a stock calibration...running lower octane in that car in those conditions would cause limp mode quickly from excessive knock sensor feedback (greater than -4 degrees timing correction on that car). I will run a few gallons of E85 with the 93 for track for extra knock supression...WAY cheaper than the race fuels Sunoco sells ($11/gal!!!).

 

[TiGeo]

Benefit in street driving?

I’m curious what you use in your modified track cars. I would assume given the turbo chargers, and the output potential of the engine, but you use some form of race gas.

Like Sunoco 260, perhaps?

Here's a good example I've posted around here before. Our VW Altas. 3.6 VR6 so non-turbo. 87 octane min. Here's 87 vs. 93 (winter blends so summer 87 would be a bit less KR - "knock retard" so the timing adjustment in degrees toward retardation based on the knock sensor feedback). So while the Atlas runs just fine on 87/gets the stated mpgs, based on these logs it should gain a little power on the top running 93 which jives with VW's manuals when this engine was recommeded to run premium showing about 10hp gain if I recall. Much less knock sensor feedback on 93 but still...has some which is interesting. Same WOT pull/same road/same conditions. I run 87 in this, juice not worth the squeeze and folks that say they can feel this are having placebo issues, I feel no difference at all between them and have gone back/forth several times.

And another for interest for my Sportwagen and the impact of running a few gallons of ethanol. This impact on hp can easily be seen by vmax (top speed) on track which would be similar to trap speed in a 1/4 run w/r to relevence to power output.

 

[John105]

I don’t think that science supports “used premium gas mileage went up.” These threads will live on for decade after decade, but the fact is octane isn’t a measure of “goodness” or “unlocked energy.” Megapixel conundrum if you will.

I ran 87 in my Nissan Maxima from 1998-2023. The vehicle didn’t turn into a pumpkin nor did it “get poor gas mileage.” In its hey day I was getting 32 mpg from smAlbany NY to Montreal on the way up. Higher than the EPA estimate.

The 2015 GTI had a label in the fuel door 91 required. Same car 2016 the label changed to 87 minimum 91 recommended.

2/3 of my cars “recommend” 91. 1/3 says 89 required. It is turbocharged.

Thanks to Costco being reasonable, I run 93 in the 2/3 cars. I don’t use 93 in the GM SUV that says 87, because it would be burning money out the tailpipe.

On the Maxima, the knock sensor did fail maybe 2015 or so—when this happened, I used premium until I could get it replaced (knuckles necessarily cut from job not pleasant). Then I went back to 87. The only ill effect from my using 87 was I didn’t get the 190/205 in the brochure. The end my .02

 

[KYMISTWALKER]

Destroy is a bit much. It won't run optimally or with as much power but the ECU should be able to retard the timing enough to manage a stray tank of 87...there would be a whole lot of destroyed engines if not. I've run 87 in an modern Audi rental with the same engine...zero issue driving normally.

Not in a turbo they recommend hi octane gasoline,

 

[KYMISTWALKER]

Not in a turbo they recommend hi octane gasoline,Unless you want your Audi to knock it’s up to you! for me I’m going to run high octane gas

You should always listen to the engineer who made it, they said 91 octane and up, if you can’t afford the extra money at the pump then why by a luxury car
It states right in the manual that Audi recommends 91 minimum

 

[TiGeo]

Not in a turbo they recommend hi octane gasoline,

I'm aware - again, you aren't going to "destroy" the engine here. I would of course run premium if they call for it but a tank of 87 isn't going to hurt it if you drive normally. The ECU will simply adjust the timing to deal with it. Agian, not optimal and if you were beating on it *maybe* you'd have some det.

 

[TiGeo]

You should always listen to the engineer who made it, they said 91 octane and up, if you can’t afford the extra money at the pump then why by a luxury car
It states right in the manual that Audi recommends 91 minimum

I don't believe I've stated that I would or recommend running 87 in a vehicle recommending 91 min - I did provide an exmpale of a rental Audi a few years ago that I used 87 in that called for 91 min. Drove it offroad/for field work/all over for a week. It didn't explode. I never heard audible knock. It ran "normal". I'm simply saying it won't "destroy" the engine. It seems you don't know how a modern closed-loop ECU works w/r to timing and knock sensors.

 

[Pablo]

It really depends on the fuel mapping. Some cars makes zero difference, other cars yes, slight.

 

[John105]

The thing that bothers me to this day. You need premium, you're a second class citizen. Why?

Even up to the mid 2000's, the spread between grades was 10 cents. In the late 90s.

87/89/premium (93 for us, 91 for CA)

$0.79/$0.89/$0.99

When gas shot up to over $3 during Katrina

$3.29/$3.39/$3.49

As one can see, the marginal % is totally different from 1998 v. 2005.

Today? Premium can be 60-80 cents more than regular, a made up price.

Luckily, as mentioned, Costco exists and is top tier. The spread 87 v. 93 yesterday was 28 cents. Not 20, but I'll take 28.

 

[Mechanician]

Not in a turbo they recommend hi octane gasoline,

Not all turbo equipped cars recommend premium.

 

[TiGeo]

Not all turbo equipped cars recommend premium.

Mine didn't. You may gain a little more timing advance with it/more power is all. Even APR offers an 87 tune for my car so more boost than stock....on 87....perfectly safe...

 

[pcoxe]

Modern cars have knock sensors. If they detect knocking sounds they retard timing. Even if a car doesn't recommend premium fuel, the reduction of knocking could allow for more spark advance and better economy and performance.

 

[TiGeo]

Modern cars have knock sensors. If they detect knocking sounds they retard timing. Even if a car doesn't recommend premium fuel, the reduction of knocking could allow for more spark advance and better economy and performance.

See post #66.

 

[Patman]

In reality when people were seeing better MPG with premium it was back when premium had no ethanol and 87 had 10%. At least that’s what it was like up here for a long while (Costco, Shell, Canadian Tire and Ultramar all had ethanol free premium up here until two years ago)

But the most you could see with ethanol free vs 10% ethanol is only about a 2-3% improvement in MPG. That’s nowhere near enough to make up the difference in price between the two.

 

[KYMISTWALKER]

I'm aware - again, you aren't going to "destroy" the engine here. I would of course run premium if they call for it but a tank of 87 isn't going to hurt it if you drive normally. The ECU will simply adjust the timing to deal with it. Agian, not optimal and if you were beating on it *maybe* you'd have some det.

The Audi dealer told me that he had a car come back and the top of the motor was destroyed by not running 93 octane, it’s clearly what the Audi dealer stated and the owners manual says
Keep running you low octane fuel ️ if it makes you happy

 

[97prizm]

I was using + for my GR86. But switching to premium Is giving me around 3 mpg better (preliminary estimate) than + gasoling. I plan on switching to premium on my Forester XT (FA Turbo) to see if the same holds true there.

Any experience here?

If your Forrester is turbo I'm fairly sure premium is recommended somewhere in the manual. It will likely pick up performance and mileage