Stay within the speed limit. Fuel economy takes a dumpster dive above 55 m.p.h., and the mileage falls precipitously as velocity goes up.
Keep your tires properly inflated. Underinflated tires hurt fuel economy, as well as handling and tire life. Maintain the factory-recommended tire pressures, although you may want to add a few pounds when the vehicle is heavily loaded.
Don't waste money. Because a lot of people do, by putting premium or midgrade gas in a vehicle built to run on regular. Conversely, use premium fuel if it is recommended by the automaker. While a modern premium-fuel vehicle will run on regular (the computer simply retards ignition), it does so less efficiently, thus diminishing power and economy.
Here are some of the wrinkles manufacturers are now employing to cut consumption:
Hybrids and electrics. Hybrids cut fuel consumption dramatically by allowing an electric motor to share propulsion duties with a gas engine. Pure electrics, like Ford's and Nissan's, use no gas, of course, but have range limitations.
Direct injection. Instead of injecting fuel into the port behind the intake valve, as conventional port injection does, direct injection sprays the fuel directly into precisely the right spot in the combustion chamber for optimum burning. That in itself increases power, as does the fact that the direct-injected fuel is cooler than a port charge would be. The resultant combustion chamber cooling allows a higher compression ratio, which, in turn, produces more power. By increasing power and efficiency, direct injection bumps up economy simply by allowing you to maintain the same speed with less gas pedal.
Automatic transmissions. Upgrades have left automatics with as good or better fuel economy than manuals. Employing more gears (Audi and Chrysler automatics have eight speeds, for example) has meant the gearing can more closely match the engine's "sweet spot," which is the r.p.m. range that maximizes fuel savings.
Engineers also have been able to get the automatic's torque converter to lock up sooner, thus decreasing gas-wasting slippage. Another nifty wrinkle is transmission heat management, which boosts efficiency by raising fluid temperatures enough to reduce viscosity.
Electric power steering. This widely employed innovation uses an electric motor rather than a hydraulic pump to provide steering assist. The latter diminishes mileage because it is powered by the engine.
Start-stop technology. This clever system shuts off the engine when you come to a stop, then starts it as soon as you take your foot off the brake. Ford says it gives up to a 10 percent fuel savings in city driving.
Low-rolling resistance tires. The low-resistance design means less friction, and that translates into better mileage.
Tire pressure monitors. They serve economy by telling you when your tires are underinflated.
Aluminum and high-strength steel. Much lighter than steel, aluminum saves fuel by shaving weight. High-strength steel serves the same purpose because you don't need as much metal to meet a strength requirement.