A. The car's size plays a major role in fuel economy, because larger cars face more air resistance, and heavier cars use more energy accelerating.

One way to improve fuel economy without changing cars is to dump junk from the trunk, said Glenn Bower, a senior scientist at the Engine Research Center at UW-Madison: "Extra luggage in your trunk, like golf clubs and tools, costs fuel every day."

More important is your driving style, Bower said, "which can improve fuel economy by up to 25 percent."

"Accelerating moderately and anticipating stop lights and stop signs so you can coast to a stop will dramatically increase fuel economy," he said.

Try obeying the speed limit instead of driving 5 mph to 10 mph faster. "Aerodynamic drag increases tremendously with speed," he said. "Try holding your hand out the window at 25 mph versus 35 mph — you should feel approximately twice as much resistance on your arm."

Bower also suggests regular "whichever comes first" oil changes: every 5,000 miles or 6 months for conventional oil or every 10,000 miles or 12 months for synthetic oil. Keep tires inflated to the manufacturer's recommendation. The owners manual will tell you when to replace spark plugs and spark plug wires. Other "tune-up" items disappeared at least 10 years ago, Bower said.

"Today's engines will detect if any other components are malfunctioning and activate the 'service engine' light," he said.

— Produced in cooperation with University Communications

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