Just bought a 91 Z28. 305 TPI. I have to fill up at least 2 times a week with only moderate driving. Getting a little pricey. What could lead to this? Does driving it hard make THAT much of a difference? I know that my throttle body is a little gummed up, but I would think that would lead to less performance, as well as less gas if anything. I previously owned an RX7, which gets the same gas mileage, so I KNOW something is wrong.

Caustic,
You did not mention your actual mileage ?? Twice a week would be good if you were driving 800 miles a week ! All kidding aside, if you keep your foot out of it, that car should get well over 20 mpg highway. A good customer of mine has a 93 Vette and he can get 25-26 on the road BUT......put your foot in it all the time, and the mileage goes away real quick. My 85 full size Blazer with a carbureted 305 averaged 16 local and 20 highway so that should give you something to shoot for. If your mileage is way off and you are driving it halfway decently, I would suggest finding someone that could put a scanner and exhaust gas analizer on it and see what is really happening.
Hope this helps,

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Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Bill:

I did not enter the actual mileage because I do not know what it is. The GM fuel sensor is so screwy you never really know how much fuel you have. Can change as much as 1/4 tank depending on your car's incline. But I drive it just as hard as my RX7, and both in top condition should get around 17 mpg or so I think. I am SURE this is not getting even remotely close to that.

Ehehe I thought I was the only one with that problem...yeah, apparently the counterbalance for the fuel gauge is either nonexistant or messed up. As a result, when I accelerate or get on an incline, fuel runs to the back of the tank, and when I decelerate or get on a decline, it drops down. It'll sometimes change from half-tank to empty on the same stretch of road.

Look at the gauge when you're driving level at a constant speed, or if your driveway is level, just leave it parked and turn on the ignition. If the fuel's had time to run back into your tank, that's the most accurate reading you can get.

BTW is there any way to fix that? It's very disturbing.