Dear Tom and Ray:

Is it true that one uses more gasoline while running the air conditioner in the car? I have a friend who insists on driving with the windows open in order to save on gasoline usage. Isn't it a health hazard to drive with all the windows down and inhaling all the gas fumes from other cars? Please advise! -- Jenny

Tom: Gee, Jenny. When I drive with my brother, the hazard is inhaling the gas fumes from INSIDE the car -- especially after he's eaten at Joe's Red Bean Burrito Emporium.

Ray: Actually, the fumes of other cars are not much of an issue in this case. Whether the windows are open or not, fumes and outside air are still entering the passenger compartment through the vents. That allows fresh oxygen in even when the AC is on.

Tom: And your friend is right that you do use more gasoline when you run the air conditioner, Jenny. Why? Because it takes energy to run the air conditioner, and that energy comes from the engine. And when you ask the engine to do more work, it uses more gasoline.

Tom: But here's the good news, Jenny. Believe it or not, at highway speed, driving with the windows open uses even MORE gasoline than driving with the AC on and the windows closed. How is that possible? Because on modern cars, opening the windows basically ruins the aerodynamics of the car. It makes it so much less "slippery," that none other than the Society of Automotive Engineers says you'd be better off with the air conditioner on and the windows closed.

Ray: What's the difference in miles per gallon between windows-open and AC- on-windows-closed? Probably not a whole lot. So it's really a matter of personal preference. But you can certainly use that argument on your friend and get her to close the windows -- at least on the highway.

Tom: But if she suddenly takes up smoking Tiparillos to get back at you, don't blame us!

Tom and Ray lead you step by step through the process of finding and buying a reliable used car in their pamphlet How to Buy a Used Car: Things That Detroit and Tokyo Don't Want You to Know. To order, To order, send (check or money order) to Ruin, P.O. Box 536475, Orlando, FL 32853-6475. You can also order online.

© 1996 by Tom and Ray Magliozzi and Doug Berman Distributed by King Features Syndicate, Inc.

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