I used a fuel additive in my 3.0 V6 for about 3 fill-ups and I got improved mileage, while trying to maintain my driving style, and driving in the same areas. Does anyone think that it is bad for the Audi engine to use a good quality additive?

 

It's not bad to use fuel additives so long as you use them exactly as the instructions as they tend to be quite strong.

The ones which tend to be bad are the oil additives etc as Audi's use special long life oil.

 

high quality gasolines (www.toptiergas.com) have more than enough detergents in them and it costs you no more to get good gas than lower quality gas.

 

Thanks for that tip. None of those fueling stations are around where I live though. I actually got slightly better mileage using the 87 as the dealership suggested. Should I continue using 92 octane or higher, or should I switch back to 87? The Audi dealer told me that since it is non-turbo that it really doesn't matter.

 

that's too bad you don't have those stations nearby. audi recommends 91+ (premium) so i'd use that. most european cars use higher octane because the compression ratio is so high. back in the day there was a rule of thumb; if the compression ratio is over 10:1 then you definately need premium to keep the engine from knocking. all audis and VW have higher compression ratios. with how advanced engine computers are now, it adjusts for the lower grade fuel but do you really want that?

i use 91 in my VW when all that's recommended is 87 and i get better milage with 91 so i figure it cancels out anyways.

 

Thanks. My mother has a 2.0T VW cc, which I believe is the same engine that Audi uses, and she just uses 87 octane because that is what the dealer put in and recommended. The manual stated high octane, but for the small amount of slow driving she does, it doesn't make a difference. Will it damage the engine?

 

actually, it's the stop and go city driving that's the toughest on engines. i would recommend what the user manual recommends. i don't cheap out on my fuel and i expect the engine to last a long time.

would i feel like i'm saving some money on gas with 87 without harming the engine? no. in the long run it could be detrimental to performance, fuel economy and possibly long term issues. when i rented cars in europe, they all required premium, and the rental agency had a policy that held me personally liable for engine damage repairs resulting from using lower octane fuels. go figure. there must be some truth behind the manufacturers recommendations.

 

Does anyone think that using 87 or 89 octane gas could harm the 3.0 engine, or just the performance? The dealer said that it will not harm it.
However, they also told me that 87 or 89 will not harm my mother's 2.0T VW CC.