I love the performance of my 04 Comp G (50,00 miles)and I didn't expect to get 30 MPG BUT the best I can do is 23 on total freeway runs. Already checked for fault codes, replaced O2 sensors, added K&N, new fuel filter, and planning to replace plugs. Also it has a short growl (feels like ABS engaging)from the front whenever I first back away from parking. Anyone have similar issues?
Thanks!!!

Sure do. I believe it was stated in an earlier thread that the "growl" is the brake pads "freezing up" and not releasing right away. Mine does it sometimes. As for the MPG, keep your foot off the gas. LOL. I just took a 400 mile trip and 24 was the best I could do.

I pulled all wheels/checked the pads. All are good, wearing even, and I re-installed them using the correct lube at the caliper mounting points. Did NOT change the growl---still could be the pad/caliper not retracting right away. I'll check if the sound is at the wheel or the ABS by walking beside. Agreed on the MPG--but still believe it can do better!?

That's what I meant to say G. It's the caliper not retracting right away. Mine did it again this morning.

My 06 does the same thing on the brakes.

As far as the mileage, I get about 22 city, and it varies depending on how fast I go. At 60mph, I get about 32, at 70mph I get about 27-28, and at 80mph I only get about 24 on the highway.

I have only had Grand Prix for 2.5 weeks now, but I am loving it.

so is there no fix for this problem?

I have searched several boards, and not found anything yet.

PCV valve, plugs + wires, if you haven't checked those already. Then maybe a seafoam / top end carbon cleaning.

I'm about to do those on my 2000GTP - hopefully that will get my mpg up too.

Regular is about to hit $3.00 here and super already has. I'm back to my 97GT running regular as a daily driver :-D

I have now had my GP since March and have done a bit of testing and after about 8-10 tanks of each in a row, I found I get better gas mileage on plain old regular unleaded than I do on 91 or 93 octane!!