Plus, an idling engine produces more air pollution. Turn off and restart your engine if you're going to idle more than 30 seconds. Combine short trips. The worst gasoline mileage is on trips of 10 miles or less from a cold start. Plan your trips and combine errands.
Consolidated trips reduce the number of miles driven.
Keep tires inflated at the psi level indicated on your tires. Underinflated tires waste fuel and increase tire wear. During warm weather, close your windows when driving at highways speeds and use your air-conditioner. For in-town driving, open windows and turn off your air conditioner. Avoid using permanent roof racks and bug deflectors that add to wind drag.