Aggressive driving (speeding, rapid acceleration and braking) wastes gas. It can lower your gas mileage by roughly 15% to 30% at highway speeds and 10% to 40% in stop-and-go traffic. Driver feedback devices can help you drive more efficiently. A recent study suggests that they can help the average driver improve fuel economy by about 3% and that those using them to save fuel can improve gas mileage by about 10%. Sensible driving is also safer for you and others, so you may save more than gas money.
Observe the Speed Limit
While each vehicle reaches its optimal fuel economy at a different speed (or range of speeds), gas mileage usually decreases rapidly at speeds above 50 mph.
You can assume that each 5 mph you drive over 50 mph is like paying an additional $0.35 per gallon for gas.
Observing the speed limit is also safer.
Avoid Hauling Cargo on Your Roof
Hauling cargo on your roof increases aerodynamic drag (wind resistance) and lowers fuel economy.
A large, blunt roof-top cargo box, for example, can reduce fuel economy by around 2% to 8% in city driving, 6% to 17% on the highway, and 10% to 25% at Interstate speeds (65 mph to 75 mph).
Rear-mount cargo boxes or trays reduce fuel economy by much less—only 1% or 2% in city driving and 1% to 5% on the highway.
If you need to use an external cargo container, removing it when it's not in use will save fuel and money.
Remove Excess Weight
Avoid keeping unnecessary items in your vehicle, especially heavy ones. An extra 100 pounds in your vehicle could reduce your MPG by about 1%. The reduction is based on the percentage of extra weight relative to the vehicle's weight and affects smaller vehicles more than larger ones.
Avoid Excessive Idling
Idling can use a quarter to a half gallon of fuel per hour, depending on engine size and air conditioner (AC) use. Turn off your engine when your vehicle is parked. It only takes about 10 seconds worth of fuel to restart your vehicle.
Use Cruise Control
Using cruise control on the highway helps you maintain a constant speed and, in most cases, will save gas.