I came across a good article about the different kinds of gas:

http://www.bankrate.com/brm/news/car...eap_gas_a1.asp

 

you're right, that was pretty good! Thanks.

 

Still won't put anything less then 91 from Mobil, Shell, or Chevron in my gas tank

 

The ONLY difference of opinion I have with teh articles author is his/her comment about gas-mileage. From my PERSONAL experiences, MY car (a '99 D2 A8, currentlywith a little over 100000 miles on the odo) gets anywhere from 50-90 MORE miles/tank on premium. This has been true since I purchased it, used, at under 50K-miles, a little over 3 years ago. This same phenomena has also been experienced by me in the past across many different makes/modelsback throughmy '92 Opel Calibra Turbo to my '87 Porsche 924, '81 735i, '81 Alfa Romeo Alfetta Quadrifoglio... And probably a few others, but these are teh cars I destinctly remember deriving a benefit, mileage-wise, from using premium gas.

The reality, in modern engines, is that the engine is smart enough to reduce the "performance" of your engine to accomodate lower-grade fuels. Lower grade fuels simply have less energy density; less BANG-for-the-buck" if you will. This can manifest itself as better effeiiency either through off-the-line performance or better gas mileage, depending on how teh engine/tranny are mated/set-up.

YOU hafta decide if teh cost is worth teh benefit. If you are unable to do so you don't deserve to drive an Audi... Drive to your nearest Audi dealer and tell them "Jazz" told you to turn in your keys. Someone from teh forums will be by to pick them up, later

edit:Aye spel four shyt

 

ROFL. I agree with you tho Jazz, I put 87 in the A6 once, and I got much shittier gas mileage than normal with 91.

 

If the octane doesn't affect performance why are there so many octance specific chips available?

I've never put less than 91 in my a4so I can't compare mileage wise but premium def gave me better mileage on my old wrangler.

 

Jackass! It might have something to do with that oil you are leaking everywhere

 

^ [sm=bustedsign.gif]hahahahaha

 

The octane does matter, just not in most cars. High performance vehicles require higher octane fuels because they burn much more efficiently and cleanly than lower grades. Your A4 is designed to operate at a level above the norm, so it requires a gasoline that burns as efficient as the car operates.

 

the octane rating actually refers to a fuels ability to resist detonation. fuel burn, not explodes, inside the combustion chamber. when it explodes you get knocking, which is detrimental to your engines internals. you can get pitting and scarring on the piston, which robbs your compression, and also when it happesn along your cylinder walls you will also lose compression. when properly ignited, under compression, the fuel/air mixture burns verrrrrrry rapidly. as the flame propogates it expands, puching teh cylinder. thousands of times per minute and we have acceleration... when iit detonates it doesn't expand properly and your acceleration suffers. cheaper (lower octane) fuel detonates more easily. modern engines sense the conditions that lead to early detonation and compensate by either allowing more fuel/air into the cylinder, which diminishes the stoichiometric ideal under which the mixture burns; or, retarding the spark, which also upsets the finely balanced act which is a fuel/air/comprssion/spark-induced ignition.

if you're gonna use cheap gas pour an octane-booster in with each fill-up.