Fuel mileage has almost nothing to do with it, but you WILL get better mileage with premium simply because CHEAP GAS IS SLOWLY DESTROYING YOUR RINGS AND PISTONS and your PCM is pulling timing, costing you performance and efficiency.

You CANNOT run anything but premium in an L67 unless you're willing to run the risk of the long and short-term damage that will occur.

How do you feel about 50/50? one fill up Premium, next regular? Im asking because Premium here in MA is about a 20 cent increase from regular.

Reg - 2.79
Plus - 2.89
Prem - 2.99

Sometimes more :?

NOT. I've had this dicussion with a couple GXP owners.( who are told by dealers it'* ok to burn Regulsr fuel) Whether you have 10-1 compression or getting the equivelent or more in boost. Predetonation is your worse enemy and you dont have to hear it for the damage to be occuring. You bought a performance machine and you should'nt let a $2 to $3 dollar difference per fillup burn holes in your pistons.

ok ok Good advice guys. I think I have to start putting some premium in her :? I'll probably be happier with the results but my pocket wont be. LOL next fill up? PREMIUM!!

Be glad it'* only a 20 cent difference. Around here it'* been 30-50 cent differences. Price gouging, because when the fuel prices have been lower, it'll drop back down to a 20 cent difference

I ran 87 once in my car, the guy filled it up with regualar, the car ran like a can of matched assshols, since that day ill always pump it myself

gas prices in canada are (per litre)

87- 108.9
91- 115.3
94- 121.7

real pricey, for a while there id hop over the border still do just beacuse of how low the dollar is and what not

^^^ Well said....premium fuel must be used in a SC motor.

if you want to play ya gota pay...

Let me sum this up.

My 95 owners manual said you "can" run regular, and if you did "do not expect full power".

When having a supercharged motor, predetonation is an issue that can occur. This means that when the cylinder is filled with the air/fuel mix and the compression stroke is in the process the charge can detonate before the spark plug fires. Hence the term predetonation. This is bad for a motor and causes damage to the internal components.

Lower octane fuels predetonate easier than high octane. The ability to run a low octane fuel is made possible in the supercharged motor by the knock sensors. There are two of these on your motor, one on each side. They "listen" for pinging (aka predetonation) and the computer in your car then reacts to the sensors and retards your timing. Retarding timing takes away power and efficiency. Meaning by running the low octane fuel and your knock sensor working with your computer to ensure the longevity of your motor, you are probably getting less power and worse mileage per gallon.

The higher octane does have a higher price and the newer series 2 cars don't state in the manual that anything else besides premium can be used.

The reasoning behind this is to maximize the miles per gallon by having the proper power from each drop of fuel.

Many members here see 91 octane as the highest available "premium" fuel available and they run that. Here in the northeast we have 93 octane availabe at nearly every station. I logged an impressive 33.5mpg on a tank of 93 octane.

While it is suggested to use the highest octane available, knowing that 91 is the best available in many places.. that might be the compromise you made. Run 91 versus 93 and know you could have more power and better mpg for a few more cents per gallon.

It all makes sense. I researched KR when I asked about it a while back and learned about predetonation. I never knew up until this point, how technical it can get just by filling up with Regular or premium.

I dont really get that good of gas mileage come to think of it.

Give your self a full tuneup then run premium....you'll be surprised