Originally Posted by monza

detonation isn't worth saving .10 per gallon...

the only reason that some of you may be getting away with it right now is due to the lower temps... once summer comes along you'll be finding a very different thing indeed.

put premium in it - with all that extra pressure you'll need the slower burning gas to help with timing... and more timing = more power (usually).

Originally Posted by Razinhell

If your going to use lower octance on a higher performance engine then you would have been better off running the non-ss version of the HHR. Boosted engines need the higher octanes to prevent pre-detonation. Higher performance engines in general run at higher compression ratio's to get those extra HP's of performance. The whole point of getting the SS was to get those 260hp's. Now you have the performance and your going to cheap out and hope that the lower octane doesn't pre-detonate. Believe what you want to believe, but the fact is Octane is gasolines ability to resist predetonation. On the compression stroke the fuel can explode before the spark plug does its job. This causes major stress on an engine as its fighting against everything else and can even cause damage. On lower octane cars the car has been tuned, tested and run many miles to work with the required fuel. In performance cars the same is true except they know that not ever where has the same fuel octane or even availability (IE California has 91 max octane while NY has 93). So when the computer detects pinging (pre-detonation) and finds that it is happening more then allowed it will reduce performance to protect the engine. I know in the LS1 and LS2 and probably the LS3, that GM produced everyone of them had this ability. Now you have a tiny 2L boosted engine. Its creating more then normal cylinder pressure, pushing way more air into the cylinder which allows it to dump even more fuel into the cylinder which allows it to create more power.

Now you can take the risk, lose some power, possible lose some MPG's as the burn in the cylinder may not be as efficient and lose some of the protection a boosted engine needs. Your also only saving $3.00+ on a 16 gallon fill up (regular to premium).

Originally Posted by Razinhell

If your going to use lower octance on a higher performance engine then you would have been better off running the non-ss version of the HHR. Boosted engines need the higher octanes to prevent pre-detonation. Higher performance engines in general run at higher compression ratio's to get those extra HP's of performance. The whole point of getting the SS was to get those 260hp's. Now you have the performance and your going to cheap out and hope that the lower octane doesn't pre-detonate. Believe what you want to believe, but the fact is Octane is gasolines ability to resist predetonation. On the compression stroke the fuel can explode before the spark plug does its job. This causes major stress on an engine as its fighting against everything else and can even cause damage. On lower octane cars the car has been tuned, tested and run many miles to work with the required fuel. In performance cars the same is true except they know that not ever where has the same fuel octane or even availability (IE California has 91 max octane while NY has 93). So when the computer detects pinging (pre-detonation) and finds that it is happening more then allowed it will reduce performance to protect the engine. I know in the LS1 and LS2 and probably the LS3, that GM produced everyone of them had this ability. Now you have a tiny 2L boosted engine. Its creating more then normal cylinder pressure, pushing way more air into the cylinder which allows it to dump even more fuel into the cylinder which allows it to create more power.

Now you can take the risk, lose some power, possible lose some MPG's as the burn in the cylinder may not be as efficient and lose some of the protection a boosted engine needs. Your also only saving $3.00+ on a 16 gallon fill up (regular to premium).