Originally Posted by Mark Hodowanec

+1 I have kept track of every ounce of fuel that my truck has consumed since I bought it. This way there are no fill up errors. Furthermore, I graph it (on excel) & use four rolling averages per graph point. This minimizes variation due to fuel quality, headwids, etc. Doing this I have a really good idea of what my mileage is. You really have to get this detailed to get good information and most people don't. At worst, they will measure it once, round up, and then tell you that they get 28 mpg. No point arguing w/ them. The better ones will measure over several tank fulls & call it good.

My truck is a 2004.5, 4x4, 6-speed, SRW w/ a big headache rack & oversize tires (tires & rack pulled mileage down a little). After 130K miles I have seen:
- overall (total 129,541 miles & 6661.1 gallons): 19.4 mpg
- best single tankful: 23.9 mpg
- best 4 consequtive average: 23 mpg
- typical winter: 18.5 mpg
- typical summer: 21 mpg

YRMV. I drive predominantly HWY & like a granny. I expect that 1st or 2nd generation truck will do slightly better, but not much.

BTW, that 6661 gallons of fuel cost me over $18K. Factoring in vehicle cost, maintenance (including tires), repair cost, & insurance: the vehicle cost represents 56% & fuel cost represents 30% of the overall cost of ownership for this truck. Clearly fuel cost drives overall vehicle cost if you keep vehicles for a long time.

Originally Posted by Busboy

There may be more to that than meets the eye. Not only are there differences between manufacturers but also between batches out of the same refinery.
We used to buy gasoline direct from the refinery for use in our aircraft. Then one day they stopped delivering to us and wouldn't say why. They just said we should call a fuel delivery service and they would deliver. After a lot of arguing and talking to different people we finally got out of them that they often make fuel that doesn't meet the minimum requirements so they "fudge" a little to get the fuel so it will at least run OK. They had only just realized the legal implications of selling us "regular leaded gasoline" for use legally in aircraft that didn't meet minimum standards by law. Do you really think they care about fuel for use in a diesel truck that will burn just about anything??

Originally Posted by wcbcruzer

I'm still skeptical, but I'm beginning to think that different brands of fuel may also play a role in mpg's. I might start experimenting with that.