ok so here we go. i fill my truck up all the way full and reset the trip. when the needle gets to the 3/4 quarter mark i look at it and its says i went 130 miles. ok not to bad. when it gets the the 1/2 mark it says i went 200 miles maybe. it keeps getting worse and worse as i keep driving. if i got 130miles between full and 3/4 shouldnt i end up getting 520 miles total instead of the 320 miles im getting now.is it the sending unit going out?

Typical.

The sending unit float is at the top range for the first few gallons, then it starts registering. If you are counting on it being accurate and linear in response, well hope you don't mind walking for more fuel! At best they are only an indication that you are actually using fuel.

jb