When you use overdrive gearing, your car's engine speed goes down. This saves gas and reduces engine wear.
Idling gets 0 miles per gallon. Cars with larger engines typically waste more gas at idle than do cars with smaller engines
Using cruise control on the highway helps you maintain a constant speed and, in most cases, will save gas.
Avoid keeping unnecessary items in your vehicle, especially heavy ones. An extra 100 pounds in your vehicle could reduce your MPG by up to 2%. The reduction is based on the percentage of extra weight relative to the vehicle's weight and affects smaller vehicles more than larger ones.