My wife and I were headed up to the top of Mount Washington last week in my truck. I had 1/2 tank of fuel at least and the trip computer said I had 230 miles until empty. The route is steep so it is advised to remain in 1st gear all the way up and all the way back down. The trip to the top is about 8 miles. The way up went very smoothly, After staying on the peak for a while (flies were biting), we started back down. At some point I looked down at the dash and saw that I had 80 miles until empty and the gas gauge was well under 1/4 tank. The next time I look, it was under 25 miles to go and I began to envision running out of gas (my wife told me she smelled gas earlier to). 10 minutes later, It was pouring rain, and now I had about 14 miles before out of gas. I pulled over to check the truck and saw nothing but got drenched. Finally we made it down to the entry point where we found a gas pump. I put 5 gallons in and then drove off. As I was watching, the gas gauge slowly moved toward 1/2 tank and the trip computer showed about 200 miles to go. Very strange huh? Any ideas?