Octane 94 vs 91??
 

Is putting 94 octane over 91 in my 06 a3 2.0t bad? can it be harmful or does it really matter? do you get better performance with 94 appose to 91?

also mixing fuels, like lets say 94 and 91, is that something that can be also bad?

I had to put regular 89? in when I couldn't get premium 93 while evacuating from Ike. For normal driving I didn't notice anything. The higher the octane the less pre-ignition (pinging) you will experience. The computer will since this and reduce timing and boost to compensate. So performance is down. Some say that milage is down as well.

Mixing octanes does no more harm than just using regular.

Where do you live that you can get 94? 93 is the best I've found here in Houston, TX

I live in Toronto Canada, the local sunoco has ultra 94 appose to shell's 91

See now if my memory is correct those in higher humidity locations get a higher octane to help with the moisture in the air. on the west coast were I have lived all my life every were I have gone the highest you can buy at the pump is 91 unless you have a race track near by or live near Woodland Hills CA were you can get 100 octane. (At the 76 station on the south bound side of the 101 right outside Agoura, for any of you in that area that didn't know about it.) And up here in Montana and our Mile High altitude the low is 85.5. I honestly would really like to know what the true reason for the east coast areas being able to have 93 octane?

Here on the Canadian West Coast, I can find plenty of 94.

There are more places than one in L.A. to get racing fuel. I use the 76 station on SanVicente in Brentwood. When I am feeling flush, I go there with a near-empty tank and buy three gallons of 100, then pull forward to the 91 pump and top it off. I estimate my final octane value in the tank is about 93-94. I notice a smoother, silkier engine feel, more effortless, somehow. I dont agree that performance is down with the better fuel...but then again, I am chipped, so engine parameters are different than stock anyway.

so if the higher octane may not help my stock car should i just stick with 91? unless i chip it

Gas Octane
 

There's no problem mixing different octane gasolines. I run 91 in my 07 A3 and it's peppy as could be and gets great gas mileage, 28-32 mpg.