octane

[harleyboy]

Is there an advantage in using 93 vs 91 Octane in 2022 S5. Is 89 Octane out of the question.
Thanks

[VVG]

Is there an advantage in using 93 vs 91 Octane in 2022 S5. Is 89 Octane out of the question.
Thanks

Good question. All depends on whether the Audi engineers designed the ECU to allow timing advance beyond the knock and exhaust gas parameters of using 91 octane. If they did, then 93 will allow more timing advance and more power. If not, then using 93 octane will actually decrease power compared to 91.

For sure, 89 octane will lead to knock if you drive hard, especially in warm air temp conditions. A certain amount of protection will be afforded by the knock sensors, but you don't want to do this too often. If you have to fill up with less than 91 octane, keep the revs and throttle application lower

[Kerbouchard]

Always use the best gas available…not worth stressing the engine to save a few cents!

[HyperM3]

You could eat McDonalds every day and survive, but how would you feel? Feed your car the best food.

[JohnEnglish]

034 Motorsports said in one of their video that unless you're running a 93 octane tune, there's no benefit to using it over 91 octane for most driving situations. If you're tracking your car or pushing it really hard where the engine gets very hot, there may be a benefit to using 93 to prevent some pre-detonation. However, for most every day driving situations 91 octane was recommended and 93 could cause incomplete combustion.

[HyperM3]

034 Motorsports said in one of their video that unless you're running a 93 octane tune, there's no benefit to using it over 91 octane for most driving situations. If you're tracking your car or pushing it really hard where the engine gets very hot, there may be a benefit to using 93 to prevent some pre-detonation. However, for most every day driving situations 91 octane was recommended and 93 could cause incomplete combustion.

I suppose it also depends on where you live. I dont see 91 at all, only 93 and then it dips down to 89. And most other places where 91 is available you dont see 93. If thats the case just get the best you can if its in the 9X's.

[JohnEnglish]

I suppose it also depends on where you live. I dont see 91 at all, only 93 and then it dips down to 89. And most other places where 91 is available you dont see 93. If thats the case just get the best you can if its in the 9X's.

Yeah, if 91 isn't available then get 93 instead of going down. Around me, the gas stations have 87, 89, 91, 93/94 octane.

[HyperM3]

Yeah, if 91 isn't available then get 93 instead of going down. Around me, the gas stations have 87, 89, 91, 93/94 octane.

Only stations I ever saw with 94 were Sunocos, but they dont have that octane around here anymore. Im a Shell/Exxon guy anyway.

[JohnEnglish]

Only stations I ever saw with 94 were Sunocos, but they dont have that octane around here anymore. Im a Shell/Exxon guy anyway.

In Canada, Sunoco was sold to another gas retailer (Petro-Canada). The Petro-Canada gas stations have ULTRA 94 now.

[VVG]

Always use the best gas available…not worth stressing the engine to save a few cents!

Okay, but how do you define "best gas". That is the issue. It is curious that the recommended fuel is 91 octane "minimum". This would seems to indicate that there may be benefit to running higher octane. But again, the ECU needs to allow timing advance from doing so, within the context of other parameters such as intake air temp, exhaust temp and knock (will it allow for timing advance until there is knock and then retard by a degree, or something like that). One would have to know the specifics of the Audi ECU, and I do not.

[HyperM3]

Okay, but how do you define "best gas". That is the issue.

Top Tier and highest octane available. Not rocket science.

[VVG]

Top Tier and highest octane available. Not rocket science.

No. If you use a higher octane than the ECU can make use of, you will lose power. The higher the octane, the less combustible the fuel. That is why the spark timing can be advanced. In the end, the timing advance favors the production of power, more than the increased octane leads to incomplete combustion, hence the net power gain if your ECU can deliver the advanced timing.

[HyperM3]

No. If you use a higher octane than the ECU can make use of, you will lose power. The higher the octane, the less combustible the fuel. That is why the spark timing can be advanced. In the end, the timing advance favors the production of power, more than the increased octane leads to incomplete combustion, hence the net power gain if your ECU can deliver the advanced timing.

Again, you arent getting it. There will be very few times youll be at a gas station with multiple options of octane in the 90s. Its either 91 or 93 mostly in the US. Under that is 89 and 87. You do not want to use 87 or 89, ergo my answer, use the highest octane available.

[HyperM3]

Yeah, highest octane isn't always the best. Higher octane just means the fuel is more resistant to pre-ignition. Putting low octane fuel in a high compression engine will lead to engine knock. Putting high octant fuel in low compression engine will lead to incomplete combustion as the fuel-air mixture will be more difficult to ignite.

Are we not talking about our cars anymore or any car being sold in the market? This is getting silly. On the S/RS forum, someone asked about the gasoline they should be using. Anything in the 90s is the correct answer as per in the fuel door and owners manual.

[JohnEnglish]

Are we not talking about our cars anymore or any car being sold in the market? This is getting silly. On the S/RS forum, someone asked about the gasoline they should be using. Anything in the 90s is the correct answer.

Well the issue was you said "highest octane available" which what was taken issue with. If 91 and 93 octane are available, 91 octane is all you need. There is no benefit to 93 octane. However, if the choices are 89 and 93 then yes, 93 would be the one to use. Perhaps a better phrasing would be "the octane closest to the recommended one without going below".

[HyperM3]

Well the issue was you said "highest octane available" which what was taken issue with. If 91 and 93 octane are available, 91 octane is all you need. There is no benefit to 93 octane. However, if the choices are 89 and 93 then yes, 93 would be the one to use. Perhaps a better phrasing would be "the octane closest to the recommended one without going below".

Use whatever you want. I have never seen 91 and 93 available at the same gas station. I think the point has been beaten to death at this point.

[VVG]

Use whatever you want. I have never seen 91 and 93 available at the same gas station. I think the point has been beaten to death at this point.

Many Sunoco stations will offer both 91 and 93. It is a widely held misconception that higher octane is better, and that is just not always the case. Whether our car, or any other, can make use of higher octane depends on the parameters that the ECU looks at to advance timing. So maybe it is the case that on a stock ECU in an RS5, there is no benefit to using a higher octane than 91....but I, for one, don't know for sure.

As far as being beaten to death, I disagree. There is lots to be learned from discussions such as this about ECU programming, fuels, environmental factors, etc. So what I would like to know is whether the RS5 ECU can advance timing to make use of 93 (or higher) octane or not? And if so, under what conditions? Lower intake air temps? Will the cooler EGT with the higher octane fuel feed back to the ECU and actuate a timing advance? Etc.

[JohnEnglish]

Many Sunoco stations will offer both 91 and 93. It is a widely held misconception that higher octane is better, and that is just not always the case. Whether our car, or any other, can make use of higher octane depends on the parameters that the ECU looks at to advance timing. So maybe it is the case that on a stock ECU in an RS5, there is no benefit to using a higher octane than 91....but I, for one, don't know for sure.

As far as being beaten to death, I disagree. There is lots to be learned from discussions such as this about ECU programming, fuels, environmental factors, etc. So what I would like to know is whether the RS5 ECU can advance timing to make use of 93 (or higher) octane or not? And if so, under what conditions? Lower intake air temps? Will the cooler EGT with the higher octane fuel feed back to the ECU and actuate a timing advance? Etc.

034 would probably be able to answer that question. However, I'm guessing the answer is no since they've already said that unlike in other cars, adding things like an intake, larger injectors, etc. will not give you any HP gains. This is because modern Audi engines are "torque request" meaning that at a certain RPM the ECU asks the engine to produce a certain amount of torque. So even if you added a bunch of power adders it wouldn't matter without a tune since the engine would still be requesting the same torque values at the same RPM. Now, the modifications may make it easier for the engine to produce the power but it won't produce more than what is requested. Those request values are all stored in tables in the ECU, hence why you need a tune to get the engine to produce more power.

[harleyboy]

I want to thank everyone for all the feedback. Gotta luv the passion …..

[Turbanator]

If there's really such a concern of timing with 93 and there's no 91 available, you can always do a half tank of 93 with another half of 89 to the same effect. In my area, most pumps are 93, it's pretty rare to see 91. I'd just go 91 whenever I do see it, and if not then 93 is the next best thing, I don't care enough to start a whole other transaction on the pump to mix with 89 and save a few cents.

[Gregory_Tolson]

i hear for the most part 87 will work with the engine being at reduced power. I think its similar to the VW Golf GTI's and R's that say use premium for full horsepower or regular for reduced. But i think even the 2.0T's in the Audis still really push 91 be used at the minimum, which suggests maybe the compression is slightly different from the top tier VW motors. Either way, using anything below 91 you have some risk of knocking which is definitely not worth taking a chance on. I think what im saying is if you ran 87 by accident one time youll be fine. Anyone have any idea if the 40 TFSI engines still need 91? Seems overkill to go premium for an engine that goes 200 horsepower.

One thing ive noticed is when i was driving my 87 octane ford fusion over the summer i was paying over $5/gal. Now im paying $3.90ish/gal for 93 with my 2019 A5, so to me it feels like im not paying any extra lol. I get id probably save $10 per fill up, but i fill up about once a week. $480 extra in gas over the course of a year and the fuel mileage its at is probably sill much better than buying a V6 or V8 car that runs on 87. Then again, does a Civic Type R run on 87?

[JohnEnglish]

Anyone have any idea if the 40 TFSI engines still need 91? Seems overkill to go premium for an engine that goes 200 horsepower.

Yes, Audi specifies premium fuel (91 octane) for the 40 TFSI engine.

[Turbanator]

Odd that the 40 TFSI requires premium. The B48 2.0T in the BMW X3 requires only 87 octane, it claims to recommend 91 but states this "has no effect on the engine life".

[Brazeagle]

I suppose it also depends on where you live. I dont see 91 at all, only 93 and then it dips down to 89. And most other places where 91 is available you dont see 93. If thats the case just get the best you can if its in the 9X's.

Very true information, same here in the NE, there is no 91 in most places.
Now...question: if I am used to 93 and suddenly go down south where there is no 93 but 91...would that be an issue with ECU memory? (mine is a 2023 RS5)
Thanks

[HyperM3]

Very true information, same here in the NE, there is no 91 in most places.
Now...question: if I am used to 93 and suddenly go down south where there is no 93 but 91...would that be an issue with ECU memory? (mine is a 2023 RS5)
Thanks

No, the minimum stated requirement in the manual and on the gas flap is 91. The biggest difference is going to be if you have a tune on your car for 93 and then run into a gas station who only has 91. You would need to download the tune for the 91 octane. Otherwise, if youre running stock, your ECU will recalibrate for the difference.