If youre talking building a hot rod motor rather than riding it like a hot rod, I find this untrue. I built an evo with 88 hp and 94 tq, ported heads with a 42 mikuni and I went from 38 mpg to 50 mpg I couldnt F'n believe it. Granted the 50 was riding in a group with stock 88's but if I got on it I could get as little as 30 or so.
I found I hardly had to give it any gas to accellerate while cruising, it just scooted down the road with so much ease it was actually less tiring to ride for 4-500 miles at a time. On a fatboy no less.

 

Probably the same service techs that swear to use Screamin Eagle parts to make real power.

 

Whatever you guys do different I respect, but nobody I know has increased their MPG doing this, taking it "easy" or not.

 

more power, more inches means more fuel

 

Not always. More power (same inches)=less throttle to move.

 

This is logical, but I changed my 89 inch stroked evo for an S&S 107 and get similar mileage, with much better performance, 102 torque/103bhp, with almost flat torque curve.