My 96 F350 gets different cruising ranges between the front and rear tanks.
I can go 300+ miles on the front tank, but when running off the rear tank I can only go about 200 miles, and often not even that far.

It doesn't matter if I use the rear tank first or not, it still gets me barely 200 miles, so I think a leaking selector valve is out of the quetion. I've filled both tanks and they seem to hold about 17 gallons each so both tanks are the same size.

The engine runs the same from either tank, no loss of power or missing, boost, temperature, all gauges show everything is the same between tanks.

Even if the sending unit was bad, that wouldn't be the cause of the mileage difference because when I fill up it always takes the same amount of fuel as the the front tank.

I'm stumped. Any ideas anyone?

 

My truck is a 97 and the front tank is 22 or 23 gallons and the rear tank is 15 or 16 gallons. I Get about 350 miles from my front tank and 220 from the rear tank.
I hope this helps.

 

the 2 tanks are different size, look in your owners manual

 

37.2 total gallons.
from my 95 window sticker

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I usually get about 18 gallons in teh front and atleast 16 in the rear if I let it run down below the red. I've ran teh rear slap out and it took 17 gallons. So the front has to be 20