I have a 93 F150 with a 4.9 inline 6 and a 5 speed. And on the rear tank I get about 13.3 MPG. But on the front tank I average 17.2 MPG.

No change in driving habits between tanks, I'm kinda scratching my head here....

 

It could be a leak. It could also be a cross-fill problem. There was a recall for certain years because the overflow from the pressure regulator would always return to one tank instead of the tank the gas came from.

 

Sounds like you need to quit wasting money on that rear tank

 

My rear tank leaks so I only use the front tank now. As was mentioned, there was a recall on the dual fuel tank Fords. Something about a bad check valve causing fuel from one tank being returned to the other causing a possible overfill with fuel spewing out of the gas cap( I've seen that ).

 

But the thing is, there is no overflow out of the truck.

 

my truck does the same thing on my 302...i can get 14 out of the front tank and 8 out of the back one.....

 

I have the same problem too, just learned to live with it. I run the front tank to 1/4 and switch to the rear and watch it drop. Within about 120 miles it's bone dry and the front tank is at about 3/4 to 7/8 full. The real problem lies within the check valve in the front sender on my truck, which should be closed when the front pump is not running, but I haven't gotten arround to feeling like paying all that money to fix it. The sender units are not cheap.

Dave