Hey Mr. Green,
My 2007 Ford Focus has given me 44 mpg on highway trips, but I want to improve its mileage even more. Is it more fuel efficient to coast down hills and ride the brakes when necessary, resulting in higher brake wear, or shifting to a lower gear and using engine breaking to control my speed? —Pokey-but-saving-fuel, in Minnesota.
Pokester, if you’re getting 44 miles per gallon with that Ford Focus you should tell the world about your driving habits and maintenance, because the EPA’s highest rating for a Focus of this vintage is 37 mpg on the highway. You are a true “hypermiler.”
You won’t save fuel by shifting to a lower gear to brake the car, according to automotive engineers I’ve interrogated. You might even use more fuel because engines have to turn faster to maintain speed when they’re in lower gears. You’re better off just relying on the brakes, unless of course the hill is extremely steep, and the brakes are failing to slow you down enough, and you actually need engine braking to save your thrifty hide. But instead of “riding” the brake, please try pushing it intermittently instead keeping your foot on it constantly.
Do not—I repeat, do not ever simply turn off the engine and coast in neutral to conserve fuel, because it’s way dangerous, thanks to certain issues, like your power brakes won't function. Even for the most dedicated hypermiler, to lose one’s life to save gasoline is too great a sacrifice.
Okay. Now you’re wondering about the EPA rating, because, while you’re widely exceeding it, a lot of drivers out there in Gridlockia whine that they're falling far below the EPA mileage rating. Well, one reason a sensible driver can beat official rating is because the EPA bases its assessment partly on the very plausible assumption that many people drive without much concern for saving fuel: They speed, make jackrabbit starts and slam-the-brake stops, and run the air conditioner when they don’t need it. Add to these follies pointless idling, surplus cargo, lousy maintenance, low tire pressure, unnecessary four-wheel-drive engagement, failure to use cruise control or to shift into overdrive on the highway, and idiotic tailgating that requires incessant braking, and, of course they fall short of the EPA rating.
For some useful tips on “hypermiling,” see CleanMPG.com. To find a whole lot of information on car efficiency, go to the EPA site fueleconomy.gov. Your tax dollars at work, unless the anti-environmentalist right-wingers in Congress defund the EPA to the point where such services are scratched.