In an effort to calculate my '92 Z-28's MPG, I filled the car to full (Actually I overfilled it, topped off with a little more than I wanted) and let it run untill the gauge empty. I eventually I drove back to the gas station expecting to shell out a good $45.00 for a full tank (factory listed at 15.5 gal), and ended up buying only 11.7 gal. The tank wouldn't fill any more. It was full! Is my gauge out of order?

 

About normal for the Fuel Gage. A little advice, Don't try to run your gas tank dry or you could destroy your fuel pump. That 4 gals is left in the tank to cool the pump and prevent damage. Additional note you don't have run it to empty for mileage calulations.

 

Thanks.

 

The typical GM gauge is not very accurate, so get used to how it works and make a mental calculation when you look at the needle.

 

Good words from blackz87
I dont think I ever saw a gauge read proper. God thing because you really dont want to be some where on empty and really be empty.
Fill the tank, maybe top it to the next nickle and check your miles. The next time fill and top of to the nickel and see how much fuel you replace in how many miles.