Burn less, save more

by John G. Smith

With fuel prices as high as they are today, any business-conscious owner/operator should have a burning desire to, well, burn less fuel. Luckily, there are steps that you can take to reduce the amount of fuel you need.

Idle talk

Comfort comes at a cost. If you’re heating your truck by idling the engine, you could waste up to four litres of fuel in an hour at 900 rpm.

Consider a truck that idles six hours a day for six months a year. If it’s on the road for 20 days per month, it could burn 2,160 additional litres of diesel. That same hour of idling also leads to the wear and tear associated with three to five hours of engine operating time at cruising speeds.

The unburned oil that passes beyond piston rings during extended idling at low rpms can dilute your oil, and that can lead to inadequate lubrication in an older engine.

Consider the use of a supplemental heater, such as models from Espar and Webasto. They use a fraction of the fuel and don’t lead to the same engine wear.

Gear fast, run slow

The popular gear fast/run slow approach on a highway truck is meant to offer highway speed at an rpm at which the engine sees the best combination of torque, horsepower and fuel economy (say, at about 1,400 rpm). With proper gearing, the approach will allow you to run at about 90 km-h between 1,200 and 1,300 rpm.

Your geared speed, for the record, is controlled by the speed of your engine, the axle ratio and the size of your tires, and should be 10 to 15 per cent more than your cruising speed.

If you spec’ such fuel-efficient equipment, be sure not to gear fast and run fast. You’ll burn any chance at fuel efficiency if you run the same engine at 145 km-h at 2,100 rpm.

Just make sure the truck maintains the startability and gradeability you need.

Follow the recommendations

Your fuel economy will improve by three per cent if you cruise along at the recommended rpm instead of 100 rpm above it.

Watch your speed

You can save between one and 1.5 per cent in fuel consumption if you drive 2 km-h slower with an excellent aerodynamic package. Drop the speed 8 km-h and you save between five and eight per cent. There’s an even greater advantage for trucks with poor aerodynamics. An 8 km-h drop in speed here will reduce your fuel consumption by 10 and 15 per cent.

Watch your shifting

Progressive shifting is a fuel-efficient way to drive, and involves changing gears before an electronic engine reaches its maximum governed rpm. You need only enough throttle to push the lever up into the next gear without lugging the engine. Simply move the lever once you have enough rpm to grab a gear.

The glide of the ride

A typical linehaul truck will improve its fuel economy by half a per cent for every full per cent improvement in aerodynamics. But not all aerodynamic improvements will offer the same improvements in fuel efficiency.

A standard roof deflector will improve aerodynamics up to six per cent, but a full roof fairing will improve them by up to 15 per cent. If you’re pulling a van trailer without these fairings or deflectors, the air is ramming into the nose of the trailer – pushing it back while you try to pull it forward. But stick to a flat-roof or mid-roof sleeper if you’re pulling a flat-deck trailer.

You’ll see another one to two per cent improvement in aerodynamics thanks to 15-inch cab extenders, while an air-dammed front bumper will yield an improvement of up to three per cent. Tractor side skirts will offer improvements of up to three per cent.

Spec’ the power you need

Excessive power means excess fuel. That’s why the foundation for a fuel-efficient engine is one that offers the power you really need, and little more.

If the world was perfect, and all roads were flat interstates, you would need less than 175 hp to move a GVW of 80,000 lb. at 60 mph. But trucks don’t operate in a vacuum, and you will face everything from grades to headwinds.

Older is better

Take heart in the fact that there is value in a truck that’s rolled a few miles. It will take about 10,000 miles for a new engine’s parts to settle in and a truck’s brakes to stop dragging, but once that happens, fuel economy will improve by anything from two to five per cent.

Source: Natural Resources Canada and Truck News files n

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