Every Chrysler product I have ever owned took forever to come down to the
full mark. My 2000 Cherokee takes about 65-70 miles, my 91 Sundance about 45
or so. I've never had one run out before Empty tho, so I am guessing you
have a float problem. The 120 miles on the Ram does sound high, I had a 97
1500 4x4, I think it only went about 40 - 50 miles before it came down to
the full mark, then dropped like a rock after the 3/4 mark, like all the
other Chryslers I've owned, my 94 Voyager was the worst.