OK, I got the build sheet for my truck using the link I found in here. According to it I have a 34 gallon gas tank. After about 260 miles the gas light on the dash started illuminating with the gauge hovering just above E. I switched the overhead to show DTE and at about 22 miles to go I filled up. It only took 26.3 gallons to fill up the tank. Does that mean I still had almost 8 gallons of gas in the tank? That's a hell of a reserve! So why is the gauge reading E and the computer telling me I have only 22 miles to empty?

 

Dodges gas tanks can be off by a 1/4 tank. Are you sure about that 34 gallon tank. Cummins tanks are that big.

 

carry a gas jug and find out how long you can go till youre completely empty

 

I don't have an overhead console, but my low fuel light comes on when I have about 7 gallons left, and I have a 26 gallon tank.

However it's always possible that your original fuel tank was replaced with a smaller tank by a previous owner. Possibly the original was damaged, and the owner came across the smaller tank cheap at a junkyard or something.

 

Like I said, the build sheet says it has a 34 gallon tank (not unusual for a 4X4 with the V10 from what I've heard) and the guy I bought it from is my best friend and had owned it since new. Says he never changed anything, but that he's run it many times well past empty knowing it had plenty of gas still left. I'm going to carry a gallon jug of gas and run it till it dies and see what the deal is. Once I determine that there is indeed another 7 or so gallons in the tank beyond empty, is there a way to recalibrate the gauge and computer?

 

that is HORRIBLE for your fuel pump.

 

I don't think so. It's the nature of the beast. The tank is long and rectangular. Which is why you notice going up hill it seems like you are losing a dramatic amount of fuel and when you go down hill your tank is rather full. So the float is pretty low in the tank even when there's a decent amount of fuel left.

 

Hit RESET on the overhead console.

 

All that will do is reset the mileage and mpg to zero. It won't correct the gauge reading or why the dash indicator comes on prematurely.

 

+1, I try not to let my gauge get below 1/4 tank for that reason. The submerged pump is cooled by the gas in the tank. No gas = no cooling = damaged pump.