Smart Driving

Max Kvidera | August 01, 2010
Kevin Koorenny pays attention to maintenance items such as monitoring tire inflation pressure and replacing air filters to maximize fuel economy on his 1996 Freightliner.

Kevin Koorenny of Redlands, Calif., has owned his 1996 Freightliner Classic since becoming an operator under his own authority six years ago. Since he’s owned it, he’s increased his fuel mileage from 4.5 to 6.5 mpg, even getting as high as 7 on occasion.

“I keep my tires inflated at the level the manufacturer recommends,” he says. “I don’t run with 95 pounds of air in my tires like a lot of people do. I check inflation every week.”

Koorenny watches his air filter and replaces it every three months. “It gets a little expensive, but they are fairly cheap. I figure a clean air filter helps the engine breathe.”

Checking tire pressure during your pre-trip routine will pay off. Every 10 psi a tire is underinflated reduces fuel efficiency by 1 percent.

Tires flex more as speed increases. Flexing leads to increased friction, higher tire temperatures and reduced fuel mileage. Rolling resistance increases as a tire flexes during motion. Cooler-running tires operating at lower speeds are more fuel-efficient than tires that run hotter.

Replacing a dual-tire setup with one extra-wide tire increases fuel efficiency 5 percent, Michelin says. Kufahl says he’s improved fuel mileage by adding wide-base tires, which are on all of his drives and trailers.

If you can afford it, buy an auxiliary power unit. Compared with burning up to a gallon of fuel per hour of idling, a fuel-efficient APU will burn only 0.1 gallon and keep you cool or warm as needed — non-diesel, battery-powered APUs are likewise on the market to eliminate fuel needed for running in-cab climate-control systems and other devices entirely.

Pay attention to your oil. Oil thickens at low temperatures, leading to increased fuel consumption. Synthetic oil is less affected by temperature, which makes it more fuel-efficient.

Change your air and fuel filters at the intervals recommended by your truck manufacturer. Regularly inspect charge air hoses and clamps to minimize air leaks that can reduce fuel efficiency.

Check your rig for proper alignment. If your tractor is out of alignment by only a quarter-degree, that sideways pull will reduce fuel economy.


Aerodynamics

A truck uses energy to overcome aerodynamic, mechanical and rolling resistance. For a truck traveling 55 mph, about half the energy is used to move air around that truck, Kenworth notes. At 65 mph, the energy usage to cut through the air rises to two-thirds. The more you can ease the flow of air around your truck, the better your fuel economy.

Depending on what aerodynamic devices you use, your aerodynamic drag will decline and your fuel economy will improve. Engineers note a 2-to-1 ratio — 2 percent reduction in drag generates a 1 percent fuel economy gain. For example, a full roof fairing would produce the greatest fuel economy improvement of 5-10 percent, while aerodynamic mirrors and air cleaners would improve it 1-2 percent.

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