1. Consider buying a hybrid, a diesel (so you can run biodiesel), or an efficient conventional car. (Aim for 40 mpg or more; the Honda Insight gets a whopping 56 to 70 mpg on the highway.) Through 2006, hybrid buyers qualify for a federal tax credit; for details, visit www.fueleconomy.gov. Or forgo a car and familiarize yourself with local public transportation routes. Some buses accommodate bicycles, so you can combine your commute and your workout.

2. Follow manufacturer recommendations for regular maintenance. Clogged air filters send a fuel-rich mixture into your engine; replacing one can boost fuel efficiency by up to 10 percent. Also, keep tires inflated to the recommended psi. Deflated tires mean more rubber—and friction—on the road, which makes your engine work harder.

3. Don’t play Mario Andretti when the light turns green. Speeding, rapid acceleration, and braking can lower gas mileage by 33 percent at highway speeds and by 5 percent around town.

4. Avoid unnecessary idling. It wastes gas and money, emits more carbon dioxide than regular driving, and causes twice the engine wear of driving at regular speeds. Idling your vehicle for more than 10 seconds uses more fuel than it would take to restart your engine, so unless you’re in traffic, turn your engine off.

5. Combine errands into one trip. Several short trips taken from a cold start can use twice as much fuel as a longer multipurpose trip covering the same distance when the engine is warm.

—S.E.E.

Sources: U.S. Department of Energy, www.fueleconomy.gov; Environmental Protection Agency, www.epa.gov; National Resources Canada, www.nrcan-rncan.gc.ca.