Fuel tank size.

Flashman wrote:
My fuel light came on in my new Ram 3500. I was near a diesel station so I filled it up - could only get 25 gallons in! It is a 31 gallon tank. Does this mean I have a 6 gallon reserve after the fuel light comes on?

I assume you mean the point where it stops counting the miles to empty to triggering the low fuel light which is typically 40-50 miles to empty. 5-6 gallons from that point sound correct. You can run it down to zero miles to empty and then you are officially on the reserve. Not that I recommend that.