If it was a medium to small 6 cyl then I believe it, but in my 99 neon (2.0 dohc 4 cyl) if I turned the air on it nearly halved my mpg at highway speeds.This chart was done a few years ago on my 1993 Chrysler Intrepid:
What I find odd about it is:
- the lack of curvature. I would have thought it would level out to the left.
- the minimal effect of the AC. It has a smaller effect than changing highway speed by 20kph.
Ive noticed for some reason 6 cyls have less of a problem with the air on.