Quote:
Originally Posted by Old Mechanic
Last Saturday I drove 150 miles to Chantilly Va. to a show, then the exact same route back home. It was cooler in the morning, about 65 degrees and as high as 84 on the trip back. On the return trip we rode with the front windows down to avoid using the AC. My brother had the passengers window all the way down and there was some buffeting so I rolled the drivers window down a couple of inches and the buffeting stopped.
The difference in mileage was .4 MPG between the two trips with the first leg at 47.5 and the return at 47.3 indicated without a reset of the readings. Traffic coming back was considerably heavier than going there and that could have been the cause of the change or at least a major factor because I managed to time the lights better after we got off the Interstate than I did coming back on the same route.
Final consumption calculation was right at 45.5 MPG, right at 2 MPG lower than the factory instrumentation.
regards
Mech
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That sounds typical. It's a trade off - but you're probably better off having the windows up and the A/C on at highway speeds. At lower speeds, it probably doesn't matter as the A/C saps engine power and the aero effects are less.
Me, I drive a convertible in summer, and I don't mind losing 1-2 MPG of FE for the fun of having the top down.
