In my 305 TBI, I don't know weather in getting like 10 miles to the gallon or if my gas guage is out of wack. I know the guage isn't very accurate because it will fluctuate from half a tank to a quarter in a couple seconds and go back up,soI never know how much gas I really have in the car. So is it a mixture of both bad gas milage and messed up guage, or one or the other. If the guage is messed up, how do I fix it and how much will it cost? If it is just bad gas mileage, how can I improve it? Thanks for any help. -Bill

 

Dont watch your milage by the gauge. I have had cars where I can get 150 miles from full to half then only 50 miles from half to empty. When the gauge says empty it could have about 3-5 gallons left.
Fill the tank until the pump turns clicks off. Note your miles. Drive and put some miles on and then fill the tank again. note how many gallons you put in to fill. That tells you how many gallons you used in how many miles.
If your gauge jumps it could be a bad sender, gauge or wire. Or it could just be fuel sloshing.

 

Yes, GM,like many car manufacturers back then did not install linear fuel guages. This made the driver believe they were getting better gas mileage than they really were. It would move slowly from full to 1/2 tank and then quickly decline from 1/2 to empty. Since the guage is moving, it's getting signal from thesending unitin the tank. I'd say it's the fuel sloshing around. The fuel level sending unit is just a small metal indicator connected to a float. As the float moves up and down, ametal indicator rides on an arc right next to a small metal band connected by two wires which changes it's electrical resistance and this is how the gauge knows where to be. As these get old, or worn, they may stick a little, or if there is somecorrosion on the metal band, the resistance may jump as the indicator sweeps and cause the guage to jump a little more. Mad Mike is right to not measure the fuel milage by the guage...this is very inaccurate. I wouldn't worry about the guage...on older cars, you shouldn't let them run too empty anyways....

 

Thanks for helpin me out. As I drive the careveryday I'm getting more of a feel for it. But my friend has got a 90' Vette with a 350 Tuned Port putting out around 300 HP to the wheels and seems to be getting better gas mileage than me. Is there anything I can do to improve my gas mileage without compromising power since this is my daily driver?

 

tune up