And as 805moparkid said:
"the motor needs to run in its rpm range first... so with a big cam hyw gears are gonna kill you... you need to be cruzing at 3 grand or so going down the road...
ive heard different theories as to is you shoulds run when the cam "cleans out" or peak tq...
i think its somewhere in the middle lol"
At 80mph im at a 2,900-3,000rpm crusing speed and Its also where I get the most tq from my engine. The gas pedal isnt pushed down much at all to sustain that speed with 2.76 gears. There is a lot more to gas mileage than just how fast you are going.