I'm getting poor gas mileage and have tried most everything I can think of. Any suggestions?

Can't hurt to try the seafoam, also. I'll try anything that's cheap.

I've just been doing a rough estimate with gallons per fill up and miles on my trip odometer. But, it seems sometimes I'm getting around 15mpg, with an average of 15 miles Highway daily. It idles rough at start up, sometimes. But, once I'm driving, it runs fine. Also, I'm going to check out the tachometer on my way to work and see what it's running at.

No check engine light currently. But, on the freeway today, it was running around 3000rpm at 60mph then dropped to between 2000 and 2300 at 70mph.

These are only 4 gear trannys that why they run so high.

At 55 mph my tach runs a smooth 1500 and im getting great gas milage! But also i don t have a heavy foot either!

I have a 2004 GA and it shifts so smooth you have to watch the tach and it will tell you when you go through your gears and when it shifts into overdrive you ll see your rpm on your tach drop around 1500 rpms at 55 or 60 mph! Im getting around 21 mpg! I guess i just lucked out when i bought it last week

Bought new 1999 grand am gt, worst car ever made. Wifes Christmas present, what a pile of crap, never has any car manufacturer ever made such a terrible automobile. Name it and it has gone wrong. Never, never, never but one of these.

Could be transmission, catalytic converter, vacuum issue, injectors, mass air flow, plugs, wires, coil pack(s), fuel pump clogging up or slowing down with age you name it... I have a 2005 Grand Prix which I'm only getting 7 MPG and have been working on it for a couple of years now on and off because I fix them and donate then to those in need like single moms with kids etc., only code it brings up is catalytic converter, but it's just a "tool car" now at work cuz theres no way I'm buying a new one or working on exhaust under "the shade tree" on the weekends ....lol.

I have a 2003 Pontiac Grand Am, when I first bought it, the catalytic converter was clogged and my car wouldn’t go passed 50 on the freeway, my father is a mechanic and fixed it, everything worked fine after that. It quit on me about 6 months after owning the car but it had 178,000 miles on it. New engines are expensive but I saved up, got a new one and it ran just fine. With my old engine I got CRAPPY gas mileage. I honestly think it’s just the type of car.