jcdb4

will be picking up my new s4 in early may and i have a question on gas. What is the lowest octane everyone is running with.Reason i ask is that i was riding with a friend who has a 335xi and he pumps 87 for around town and 91 or 93 when he is roadtripping. Any thoughts? Can 87 cause damage to your engine? thanks

B8aruba

Any high-performance engine benefits greatly from higher octane content fuel. Not only will the engine make more power, but it will also run cooler in the process. Almost all VAG engineered power plants are high-compression, especially those which are forced-induction (turbocharged and supercharged). The most efficient combustion is produced using higher octane molecule content fuels, but be aware not to run too much octane. Too much octane can also damage an engine if it's not designed to run it.

I've always run the highest octane pump gas I can readily find (usually 92-93 R+M/2 here in the Midwest). However, always follow the recommendations from Audi as listed in your owner's manual. IIRC, they recommend premium octane content for almost all their engines. Stay away from 87 octane with that engine, especially when stopping/starting often (i.e. city driving), accelerating hard, driving in high ambient temps, etc. These conditions, when coupled with lower octane fuel, can lead to pre-detonation and misfires. If you want that engine to run properly, run premium. If you can't get the min octane level you need in your area, consider an octane additive as a last resort. Just be sure you know how to mix it properly.

NWS4Guy

92, that is the lowest I run because it's the highest I can get here.

ShadowJet

Read this article someone copy pasted in the A4 forum in regards to Octane.

https://www.audiworld.com/forums/sho....php?t=2777936

B8aruba

Don't be misled by the opening statements in that article. Read on, and you'll find out why it's so critical to run higher octane fuel in the 2.0T and V6T engines in the A4/S4. It's no joke, and can make all the difference in the world in high-compression engines.

ShadowJet

The ultimate conclusion of that article should be...

"However, more aggressive engine management schemes, especially those found in turbocharged or supercharged vehicles, can turn up the compression to a high level, requiring much higher octane gasoline to avoid knock."

IAS5

car recommends 91 minimum- use 91 minimum.

jcdb4

thanks for the info and the article.

HyperS4

No offense, your friend with the 335 is an idiot. Especially since he uses the crap gas for around town which exhibits more wear and tear on the engine than highway driving.

McGriddle

I use only 93 octane.