hi,
i have a 2005.5 audi S4 and was wondering if i could get away with putting regular gas in there or not.

honestly, i don't really care about the 30 or 40 extra horse powers (if that) that i would get with a supreme gas grade....i care about the overall health of the car/engine, and whether putting regular gas would hurt the car in anyway.

please let me know.

ps. this is NOT a lease car, so i do 'care' about the car.

 

I know that the basic principle of Octane is the resistance to detonation (commonly referred to as engine knock), where as we want a slow controlled burn (combustion) of all gas in the cylinder.

Using a lower octane gas in a high performance engine can cause damage overtime (if not immediately, depending on vehicle...correct me if I am wrong) due to the detonation caused, thus increasing the pressure in the cylinder. Most of these higher performance engines that recommend a higher octane gasoline most likely have higher compression pistons, thus by using a lower octane gasoline will shorten the lifespan of the engine, if not causing some sort of premature failure.

 

^^^
reasonably accurate

Anything less than 91 octane and you are risking damaging your motor

 

thanks guys. i went to costco and got gas yesterday. i bought the 93 grade premium.
they also had the 87 that just said "unleaded".

now i was thinking....the 93 that said Premium, didn't say "unleaded"! is that just assumed?

also, is 93 sufficient?

 

yes, minimum recommended octane is 91.Always a good idea to not stray away from mfgr's. ratings.

 

I believe nearly all gasoline in the United States is unleaded as of the early 1970's due to its toxicity to the environment when burned releasing lead into the atmosphere. Most street driven cars with catalytic converters use Unleaded gasoline only.

 

Yes, leaded fuel is illegal for on-road use in any year vehicle (at least in this state). Do have a station near my house with 110 octane but it's cleary labeled "LEADED RACING FUEL OFF ROAD USE ONLY" and you must pump into a can OR into the race car on the trailer.

Using 87 octane in your Audi won't cause damage per say. The knock sensors will keep any detonation away BUT it will cost you more in the end. The mpg using 87 will be substatntially lower than using 91-93 octane. Also, 87 normally doesn't have the detergent levels the premium fuels have which will cause valve deposits, dirty injectors, etc over time. You have an 11:1 compression ratio so use ONLY 91 or higher and you'll be money ahead.