I'll have to agree with you, I should have said most of the time as you stated, that you want to "have the car the MAJORITY of the time in the power range." I did a test in my '56 Chev with the 302. I had 3.08:1 gears in the rearend (good highway ratio) with a TH350 tranny. I was pulling about 16 mpg which I thought I couldn't get much better. Then I had a friend who wanted to swap pumpkins in the rearend. I had wanted a little more off the line power with the 302 so I traded his 3.70:1 set for mine. It bumped my cruising speed into the noticeable torque curve of the cam, and cruising at 3500 rpm I pulled 20 mpg (no bull$#@%) on a road trip once. Another test was with a friend's '57 with a 406sb and 700R4. This engine is a torque monster at low rpm, and his car is geared such that he's running 1800rpm at cruise speed, logging 17mpg. So yes, depending on the motor, you want to be within the bounds of the working torque curve. The 302 probably has a peak somewhere near 5500rpm which certainly wouldn't be gas mileage friendly, but the 406 has a torque peak at much much lower rpm. And the cam choice has alot to do with that.