Yes it steals power no matter engine size, so you will have less power and in turn reduced MPG. So does your alternator, that's why when you race you should have everything electrical turned off along with the A/C. A little fun fact, if you're aiming for the best mpg roll your windows down if you're going under 35 or so and use A/C above that. Also the when you use the defroster or recirculate the A/C is turned on automatically.
2006 Red Chevy Cobalt LT
mods: Kenwood DNX5140 Head Unit, HIDs, Halo headlights, LED taillights, Injen CAI, LSJ throttle body, 2.4L intake manifold, red interior LED's, TWM short shifter, custom fit red seat covers, red trim and door handles, SS gauge cluster, Racing Solution long tube header/downpipe, Corsa touring exhaust, lightweight crank and alternator pulleys, trifecta tune, 17" Motegi black rims