Michael@Parker

Curious because this is a typical question that I recieve from customers. Correct me if I am wrong, but by not using premium unleaded, does this make your car prone to more carbon build up?

If not, what would be the issues as a result of using regular unleaded fuel?

Jacon

The possibility of detonation which over time destroys the cylinder walls and pistons resulting in pre-mature failure of engine components...it's bad stuff

CEB

.....VW and Audi are now "recommending" (they used to say "requires") 91 octane fuel (in the US - octane numbers are different in the various countries) and you shouldn't use less than 87 octane (again, using the US way of measuring octane). Using 87 octane will result in less power as the computer dumbs itself down to use the lower octane - the extra power will return when you use 91 again.

That said, lower octane gas could lead to decreased gas mileage as well but it won't cause any damage unless your car is "pinging."

CEB

...if the computer can't compensate for the lower octane. It should have no issues with 87 octane.

tubi

I didn't notice decrease in gas mileage either on my B7 2.0T. I switched back to 93 octane eventually as the car feels sluggish on 87.

need_TQM

These engines have knock sensors to prevent detonation, which is agreeably very bad for parts, but unless you put something below 87 octane in, the engine controller will retard the timing appropriately to prevent detonation. The cost will be a loss of a bit of power, and possibly slightly higher fuel consumption. Have not heard numbers on the 2.0T, but Hyundai's Genesis V8 is rated at 310HP on premium and 306 on regular octane.

Audi recommends, but doesn't require, an octane of 91 AKI/95 RON.

It does REQUIRE a min octane of 87 AKI/91 RON. It further states that using 87 AKI will "slightly reduce engine performance"

Mobilehavoc

Slightly related to this is are there any real benefits to using 93 octane? Since I've had the car I've only ever used Shell V-Power 93 octane gas because it's on my corner and my trips haven't been long enough to gas up away from home.

Is it worth it using that or is 89-91 octane sufficient?

Bob58

The emphasis there is on "may" and "slightly".

Personally, I never really noticed any perceivable difference in performance on my previous 1.8T, 2.0T or current 3.2 between 91 and 93 octane.

All have been stock.

With modified software, the ECU will be able to take advantage of the higher octane ratings to advance timing but you lose the capabilty of running fuel with less octane than the rating for the program.

Personally, I run Shell 93 because that is what is readily available and of very high quality.

If all that was available was 91 AKI, I wouldn't sweat it in the least. Worst case, you'd be getting 99.5% of available performance from your engine in stock tune.

dk1

Has anybody actually tried 87 octane gas on a B8? I have been using 93 Shell gas so far because prices are low and it is recommended. But I think gas prices will inevitably go up and it's nice to know how performance and gas mileage would be affected if 87 gas is used.

markcincinnati

Slightly less: Power and Fuel Economy and somewhat higher risk of ping although that should be mitigated by the electronics.