Im getting really really bad fuel milage

[wiserocz]

What is considered good mileage? I got over 330 miles on a tank with my Achieva 3300 now with my Monte its around 240 or so, but thats before I changed my o2 sensor I'm going to see what I can get this next week.

[MIGUEL]

milage

I HAVE A 3.4L 95 CUTLASS SUPREME THAT I HAVE OWNED FOR 4 YEARS. IN THE BEGGINING I WOULD GET ROUGHLY 450KM-470KM PER TANK (ACCEPTABLE).AFTER TWO YEARS 400KM A TANK (OK). IN THE LAST 18 MONTHS MAYBE ON A GOOD WEEK 300KM PER TANK(WISH I HAD A HONDA). MY CAR IS IN TIP TOP SHAPE, WITH LOTS OF POWER. REPLACED EVERY SENSOR WITH EXCEPTION OF KNOCK AND O2. IAM BRAINBOOGLED, BUT I HAVE READ IN THE FORUMS OF SOMEONE REPLACING THERE DRIVE BELT AND DOING THE CAM TIMING, SOLVED THE PROBLEM. DID YOU DO THE CAM TIMING WITH YOUR REBUILD? IF SO WHATS LEFT KNOCK SENSOR? IF YOU SOLVE YOUR PROBLEM PLEASE POST IT BECAUSE I CANNOT HANDLE 300KM PER TANK, BETTER MILAGE ON A HUMMER OR MONSTER TRUCK...

[pepsi_coke]

No need to yell!

[SappySE107]

The timing belt will stretch ofter a couple thousand miles, which throws the timing off a few degrees. I haven't had much issue with this as I pull my belt quite often, but the gas mileage could be from this. Not a whole lot most people want to do to get a few MGG though unless you have the time and tools to do it easily.

[grandprixgtp_91]

well the place that rebuilt the engine did all the timing on it, they didnt use gm equipment, its all napa, but i did check the timing before installing the motor and it was right on. my guess is the injectors now, maybe the knock sensor, but i dont have a reader to hook it up to to see, i wish i could use my laptop for a scan tool.

Jake

[OldSkoolGP]

Another thing you guys could check is your brakes. I know it sounds weird, but I had a friend who was dragging a rear caliper and it was killing his gas mileage. Also check your parking brake to make sure it is fully disengaged. Also, what kind of plugs are you running in your motor?

[grandprixgtp_91]

well its not the brakes, they have been replaced about a thousand times and it rolls perfect, and the type of plugs ar AC delco, they are all i will use in this engine.

Jake