Well I filled my tank up tuesday, and today is sunday and it says I haven't even used a quarter of a tank. I usually go through around a half a tank by now.

I have the dual tanks, and I ran on my second last night and it seemed as if it went down some but when I switch to the first tank it stays at where the 2nd is now.

I just replaced the fuel filter a month ago when I bought the truck. How can I check and see if the gage is bad or what?

I have 1991 F-150, E4OD, I-6.