GTP using lower octane
 

I have owned my GTP for about a year now and the previous owner claimed he never ran premium fuel. He also said he has had no issues because of it.
I have read that the supercharger will not operate properly without premium. (loss in performance) Will running regular fuel hurt the supercharger or engine?

I believe that the biggest threat is heat. Higher octane generates less heat. That's why a lot of those 3800 guys run cooler t-stats (sometimes drilled) and 104 plugs. If you're not rodding the pi$$ out of it you probably won't have any problem. Remember that when you run regular gas, KR goes up and power is enormously reduced by the PCM.

I would think that this is counter productive.
A larger pulley would help too as KR is real high running regular.

FWIW my GTP pinged big time on regular when I got into it. I only ran one tank and switched back to premium. Most of my driving was between 4k and 8k elevation which should lower the CR and performed better on regular. I think GM recommends premium for a reason.

I am sure that the recommendation is there for a reason like you said milkcrater. Thanks for that info on your GTP. I am in MI and have not had a spark knock issue yet. This car is my daughters next year and its not in the best of shape. Its got 155,000 on it and I am sure she will be taking out the mailbox as soon as she gets that permit. LOL. (gotta love teenage drivers) I was concerned about a saftey issue like that extra exhaust heat like ohmygoat talked about pluging the converter and start that thing on fire. Which now seems possible. Until then I will keep my foot out of it.

'04 GTP since new, 50K miles, excellent shape. Ran 93 Octane Premium when new, just because. After about 2 years and when Premium 1st crossed $2, I said, I'm not paying $2 for gas (LOL!) and started using 87 regular. Have never put premium in it since.

I don't kick in the SC much at all, maybe when merging onto highway. But never had a ping. I'm in Fla (sea level) and until about a year ago we did not have ethanol. Now that is all I see ("up to 10%").

Only thing I've noticed, was always getting 24.5 mpg highway, on ethanol it seems to be consistently lower now, closer to 23 mpg.

I'd have to go read the Owner's Manual, but I think it is one of those deals where it will make most HP on premium, the computer will dial it back on lower octane. Since I'm not racing this car, I'll pocket the savings instead. Seat of the pants, I can't tell any difference when the S/C kicks in now vs. on premium.

If you have an older Gen S/C, your results may be different.

I've got a '99 GTP I bought new. It has 218,000 miles on it. My wife drives the p*ss out of it. I have always used Premium fuel. I have never had an engine problem or fuel related problem. I still get around 24mpg around town and 30 MPG or better on highway trips. Other than replacing a couple of pulleys...not on the SC...and routine maintenance I have had very little problems with it. Though, I did replace the transmission at 200K miles. It was starting to slip and a reman. trans was the best option for the SC engine and came with a 100K warranty. When gas prices skyrocketed, I too looked into using the lower octane fuel. After my research, I decided it was worth it to me to pay the extra for prem. fuel. I have never had a problem and based on what I read, I thought it was a worth while expense. A small price to pay for power, and power is what I want when I want it! :) 218K and counting...I am happy and still no problems. It's a great car and plan on keeping it.