Can energy spent by mechanically sucking or blowing air be compensated by lower drag?

[freebeard]

I say simply, it depends on your starting point. If you're starting with a brick, then maybe you can get beyond a break even point with an active device... They think that if a brick gets 50% better mpg by putting a kamm on it, they should be able to get 50% better mileage putting a kamm on an already reasonably well designed car.

GTRI went the other way.

Recent experimental results obtained by GTRI using blowing have shown drag reductions of 35% on a streamlined automobile wind-tunnel model. Also measured were lift or down-load increases of 100-150% and the ability to control aerodynamic moments about all 3 axes without any moving control surfaces. Similar drag reductions yielded by blowing on bluff afterbody trailers in current US trucking fleet operations are anticipated to reduce yearly fuel consumption by more than 1.2 billion gallons, while even further reduction is possible using pneumatic lift to reduce tire rolling resistance.

"...using pneumatic lift to reduce tire rolling resistance" reminds me of Bucky Fuller and Jocko Johnson.