I have a 400 sbc and I get about 5 average. On the highway if I keep my foot out of it I can squeeze 9-10 out of her. I have 35" tires and 4.10s currently. Can't wait to put my 4.56 gears in her
I also have a TH400 tranny and no overdrive. When I have the 700R4 and the 400sbc I got about 10mpg. Generally off-roading I measure it in Gallons Per Mile
How about some specifics? What kind of truck do you want to know about? Do a search for this (on both the SFA and IFS boards) and you will definately get a bunch of answers. 95 K2500 350/NV4500/3.73's/33" tires 13-15mpg city, up to 18 on the highway going 60-65mph. 13 or so going 80.
78 Chevy Blazer with a 350, SM465 4 Speed, 35" MTs and 3.08s[img]images/icons/shocked.gif[/img][img]images/icons/crazy.gif[/img]... somewhere in the neighborhood of 7-9 mpg... I'm just waiting on the cash to upgrade my axles to 1tons and 4:56s...