need alittle help

what kind of truck is it, give me all the specs of the truck so we can work with you. here is a common study done last year, on a typical truck, on flat ground with no head wind, its takes 250hp to move 80K lbs at 55mph, to move that same load at 75mph it takes 400hp, the more hp you use, the more fuel you use. what kind of engine to you have? we can help you out, just need more to go on. I typically dont run the 63mph in my local trucks because of the gearing, and no more than 70mph with my over the road trucks. My pete gets 5.9mpg and and my mack gets 6.5-7mpg, those are both over the road trucks. My kw local truck gets 5.7mpg, hope this helps

 

I seem to do well at 60-65 mph. You don't want to lug the truck down. The type of terrain can have a big impact on your mpg. I drove from Oregon to Tennessee once and checked my fuel mileage at various speeds. It helped to get a good idea of the differences. I was surprised that there wasn't as much difference as I expected. I usually drive at 60-65 mph and that seems to be a good range for me.