Max a/c position only shuts off outside air intake thereby solely recirculating cabin air, no inherent change in energy consumption. Change in blower sound is simply due to this more restrictive change in air routing in the plenum.
Up to 10% decrease in mpg would be my guess in general driving, less on long highway run. I've never done a measured run comparison.
98 Mystique LS v6 atx 110,000km
97 Contour LX v6 atx 125,000km
stock CD on LS, cass on LX
spoiler, tinted windows on LS only
4 wheel discs on LX only
All other available options on both
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