Plan ahead to accomplish multiple errands in one trip, and whenever possible avoid high-traffic times of day. If you own more than one car, use the most fuel-efficient model that meets the needs of any given journey. Remove unnecessary and bulky items from your car. Minimize your use of roof racks and remove special carriers when not in use. It takes more fuel to accelerate a heavier car, and the reduction in fuel economy is greater for small cars than for larger models. Minimize your use of air conditioning. Even at highway speeds, open windows have less effect on fuel economy than the engine power required to operate the air conditioning compressor.