Trucks: Maximizing fuel economy

Fuel prices are up. And it doesn’t look like they’ll go back down any time soon. Here’s a refresher course in maximizing fuel economy in heavy-duty diesel trucks.

Before you leave the yard
Chuck Blake, manager of special projects, Detroit Diesel, says to successfully counter high fuel prices, your drivers should spend a few minutes walking around the truck making the following checks:

· Inspect the truck for any oil or coolant leaks.
· Pressure check (don’t just thump) all tires to ensure correct inflation pressures at least twice a week.
· Check for irregular tire wear (a sign of axle misalignment, which negatively affects vehicle mileage).
· Check engine oil on a level surface before starting the engine.
· Check over the charge-air-cooler and its hose connections for trace soot marks between the tubes and header. Any soot traces on the engine or close to the exhaust manifold should be identified to maintenance.
· Check the radiator’s exterior surfaces and make sure they are clear of road debris. Hose out the bug screen if necessary.
· Check all fan belts for cracks and missing ribs.
· Check the integrity of the radiator fan shroud: make sure it’s in one piece.
· If the air tanks are drained, make sure the drain valve is completely closed.
· If the fuel filter is mounted in a see-through bulb, make sure the fuel level is close to the top of the filter.

Behind the wheel
Once the walk-around is complete, you can start the truck, but there’s still a lot to do to maintain peak fuel consumption. Start by minimizing vehicle warm-up times. Once the air pressure gauge shows the system is fully pressurized, the truck is ready to go. Avoid any hard throttle inputs until the correct engine operating temperature is reached.

Now is a good time to run a quick brake check. Auto adjustment systems can take too much slack out of the brakes in failure mode, creating drag and dramatically affecting fuel economy. Make sure the brakes don’t “grab,” and that the truck rolls freely once they are released.

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“On hard, level surfaces, learn to engage the clutch with no throttle input,” says Russ Siegel, specialist, truck operations, Caterpillar On-Highway Engine Division. “This technique, known as ‘spot-shifting,’ allows drivers to use second gear when the truck is loaded and third when empty to get moving using just enough throttle and rpm to engage the low side gears.”

Blake suggests learning to upshift the transmission well below 1,500 rpm on the low side and gradually work the engine speed faster on the high side, shifting between 1,500 rpm to 1,600 rpm maximum. “Make the engine pull and work peak torque speeds,” he says. “Full throttle accelerations tend to decrease fuel efficiency, but full throttle pulls cresting grades make sense. Learn to anticipate speed reductions and plan for stops ahead of time and leave the transmission in gear and avoid downshifting if the light has just changed to red.”

Slower speeds are better, Siegel notes. Running 65 or 70 mph in a vocational application saves you only a few minutes on your schedule. But the engine burns a lot more fuel, particularly in urban settings or hilly terrain. “I don’t think a vocational truck ever needs to go faster than 55 mph in urban settings,” Siegel says. “A smooth, steady cruise at those speeds going with the flow of traffic can quickly increase a truck’s fuel efficiency.”