Tactic No. 4: Cruise at a Slower Speed
Since the power required to overcome aerodynamic drag is a function of the velocity cubed (in other words, it shoots up quickly), a car's jump from 40 to 60 mph requires less fuel than the increase from 60 to 80 mph.
Tactic No. 5: Climb Slowly (When It's Safe)
Imagine driving on a flat highway and approaching an overpass. From a fuel-efficiency standpoint, the best strategy is to turn off cruise control and forget about maintaining a constant speed up and down both sides of the grade. But we'll save it for lightly traveled roads.
Tactic No. 6: When Coasting Downhill, Leave the Car in Gear
There are those who refuse to be shaken from the practice of coasting downhill in neutral to save gas. This is a bad idea no matter how you look at it. Let's set aside fuel economy for a moment. Coasting downhill in neutral is illegal in most states. And it's dangerous in all states. In neutral, you have no way to accelerate to avoid a hazard, and if the engine stalls, you have no power steering or vacuum boost for the brakes. If the hill is steep enough to call for hitting the brakes to keep you from gaining speed, they're more likely to overheat—and overheated brakes lose effectiveness until they cool off. They'll probably do that right around the time the police show up to take the accident report.
Fuel-Sipping Basics
Monitor Tire Pressure
Keep your tires properly inflated, because low pressure increases rolling resistance. Few drivers check and adjust their tire pressure often, but it's a good idea to do it once a week.
Plan Errands Carefully Reduce the miles you drive by running all your errands in one trip. Making a run to the dry cleaner and then picking up the kids after soccer practice? Don't make separate outings. A little bit of foresight will stretch your fuel economy.
Warm Up the EngineCars get better fuel economy when the engine is warm. So if you have a three-stop run, hit the farthest destination first, then work your way back home. A fully warmed-up engine will remain at an efficient temperature even if it's parked for 30 minutes.
Make Right Turns OnlyFedEx does it, and the MythBusters proved it works: When city driving, make as many right turns as possible, even if it means going a few hundred yards out of the way. Reducing loiter time—or idling while waiting for traffic to clear—saves gas.
Avoid Ethanol When PossibleGasoline that has been cut with 10 or 15 percent ethanol, called E10 or E15, is an mpg killer. Why? Gasoline stores more energy than ethanol (119,000 Btu per gallon vs 80,000). So it takes more ethanol than gasoline to go the same distance.