Bottom Line
Modern Trucking Techniques
More miles
Getting the best fuel mileage possible takes a lot of knowledge and discipline

Paul Abelson
senior technical editor


"From now on, we will think of $2-a-gallon diesel as only a fond memory."

I first wrote that statement when fuel was approaching $3 per gallon, and barring any drastic changes in the economy or world situation, I stand by it today. Fuel always has been a major factor in any trucking operation's profitability, and now its impact has more than doubled.

How, then, can truck operators control fuel costs? By individually managing each factor that contributes to fuel use - everything from equipment to driving style, maintenance to purchasing. If you have not been managing everything before, now is the time to start.

Speed is a major factor in fuel consumption. Kenworth publishes a table that shows the effects of speed on fuel economy. Going 65 mph compared with 60, there's a 6.4 percent decrease in fuel economy. Comparing 70 to 60, the decrease is 10.9 percent. At 75 mph, the difference compared to 60 is a whopping 17.3 percent.

Plan ahead
But how can you drive at only 60 mph and still make your deliveries and make money?     

Jim Booth, a retired senior applications engineer and development driver from Caterpillar, not only knows how to do this - he does it on a regular basis.

Booth operates Fifthwheels Plus, a small fleet in Wataga, IL. He's made numerous presentations at the Technology & Maintenance Council conventions and other industry events and is acknowledged as an authority on maximizing fuel economy.         

In August 2005, Booth personally achieved 9.2 mpg, while his drivers running all across the country averaged better than 8 mpg.

"Getting good mileage starts with route planning." Booth said.

"I check the atlas, then go to the computer and compare routes. I may have to put in waypoints to check a route I see on the atlas. If I can go on secondary routes, I may have to drive slower, but usually I can avoid big cities and their congestion, and the routes I pick are more direct.

"I don't mind going 55, especially if I can save 60 or 70 miles. I rarely go over 60 on the interstates, anyway." 

Booth plans his route and his time.    He sees no reason to drive faster than necessary.

A great case in point is when Booth was being interviewed for this article on a Monday morning.

"I'm on my way to San Diego. I'm scheduled to unload Friday morning. The route they gave me pays on 2,045 miles. My way, it's only 1,985, and the route is farther south. Warmer air is less dense, and that helps mileage, too," he said.

"When I did some testing for Cat, we observed about a 4 percent fuel economy improvement for each 10 degree temperature rise."

TMC, however, indicates the difference may be only about 2 percent per 10 degrees.

Get good fuel
According to Booth, fuel quality has improved since the introduction of low-sulfur diesel and that has helped fuel mileage as well.

"Cheap fuel doesn't necessarily mean bad fuel anymore. I have a network of low priced fuel stops that I use regularly. I know they sell good fuel. They're in my computer favorites along with all the chains," he said.

"When I'm planning my route, I plan my fuel stops, too, to get the best prices. You can find prices on the Internet. I buy only enough to get me safely to my next planned stop. That way, I'm not carrying the extra weight of fuel at 7 pounds per gallon."

Slice through the air
Aerodynamics play a big part in fuel economy. A truck's coefficient of drag is the sum of many factors. One rule-of-thumb often mentioned at TMC is that all things being equal - of course they never are - a fully aerodynamic truck will do roughly 1 mpg better than a classic tractor.

TMC Recommended Practice RP 1111, Relationships Between Truck Components and Fuel Economy, indicates that shortening the gap between tractor and trailer to 25 inches can save from a half of a percent to 5 percent, depending on where it was set.

Air deflectors can save up to 6 percent, while a full roof fairing can save up to 15 percent. Other aerodynamic savings include: cab extenders, up to 2 percent; contoured air dam front bumpers, up to 3 percent; tractor side skirts, up to 3 percent.

RP 1111 also states that switching from lug-type drive tires to rib-type can improve mpg 2 percent to 4 percent. Worn tires, with less mass to flex, can be 5 percent to 10 percent more fuel efficient than new ones, so expect a drop when you replace tires.

Turn it off
Idling is a big no-no if you want maximum miles per gallon.

Last issue, we reviewed alternatives to idling. If you can get 6.5 mpg driving 550 miles in a day, then idle 10 hours using 0.8 gallons per hour on average, those extra eight gallons take you from 84.6 gallons up to 92.6 gallons. That drops your average fuel mileage to 5.9 mpg. At $2.50 per gallon, idling costs you $20 per day in extra fuel alone, or $100 to $120 a week.

That's more than my gross pay on my first job.

Idling cost varies with the number and type of devices you run, such as your air conditioner, fans and hotel loads.

Remember, anything that consumes energy uses fuel. Even if you don't idle and you use deep-cycle batteries and an inverter to power comfort accessories, you have to "pay back" that energy by recharging the batteries.

But recharging when the engine is already turning, doing the useful work of moving the truck down the road, it doesn't need extra energy to move pistons, pump oil and coolant and turn gears. It does when the only reason the engine runs is to provide comfort when the truck is stationary.

Driving right
Driving technique plays a huge part in fuel economy. According to fleet reports incorporated into RP 1111, the difference between the best and worst drivers can be as much as 35 percent.

Some drivers have to lead the pack away from each traffic light. Some have to charge up the exit ramp, braking heavily at the stop sign. Others ease away, practicing progressive shifting and coast as much as possible before reluctantly applying their brakes. Which ones get the most out of each gallon of fuel?

Booth teaches drivers to stay as close as possible to the engine's optimal rpm.

"Use cruise control as much as possible," he said.

It keeps you at a steady pace, avoiding unnecessary acceleration. His C-15 Cat 4550 is rated to have peak torque at 1,200 rpm, but the torque curve shown on the Internet shows it being available at only 1,000 rpm. It remains level to 1,500 rpm.

Booth checks his computer regularly, monitoring his own driving practices. The month he exceeded 9 mpg, he averaged 1,103 rpm for more than 25,000 miles. By gearing fast (3.25 rears) and running slow - 55 to 60 mph - he kept the engine propelling the truck, not churning the pistons.

Proper maintenance
The final step in maximizing fuel mileage is maintaining the truck properly. Keep tires aired-up, not just for tire life, but also for fuel economy. Low pressure lets tires flex excessively.

The energy to flex the tire comes from the fuel the engine burns. Flexing converts excess energy to heat, which is lost to the air.

Out-of-alignment tires drag tread sideways, as much as 50 to 100 feet per mile. It takes energy to do the dragging, energy that is consumed scrubbing rubber off the tread. Poor alignment shortens tire life and uses energy unproductively.

Synthetic oils don't thicken as much as mineral oils when cold. Not only do synthetics extend drain intervals, they put less drag on the engine, lessening the fuel-robbing effects of cold weather.

The right mindset
Most of all, improving fuel economy is an attitude. If you want to save fuel, you will. You'll shut the engine off when you're not moving. You'll keep your equipment in tip-top shape so it doesn't waste fuel.

If you operate for maximum fuel economy, you'll be putting thousands of dollars more in your pockets each year. And if you do, you'll be among the elite of the trucking population.

As Booth has observed over the years, "The problem is that 95 percent of the drivers don't care, and the other 5 percent are already doing it."

Which group are you in?

Paul Abelson may be reached at


Progressive shifting

As little as 25 years ago, diesel engines had relatively low power outputs per cubic inch of displacement. In order to get acceptable performance, drivers had to take their engines to redline with every shift.

Today’s engines and transmissions don’tneed to be wound up like yesterday’s. The most economical way to drive a new engine isto increase rpm in first gear to only 1,200 rpm,then shift up.

You’ll catch second gear at around 800 rpm. Because you’re already rolling, you don’t need as much extra torque to accelerate. Second gear has less multiplication than first.

The electronic engine controls will keep you accelerating smoothly. Make your second to third shift at 1,300 rpm, third to fourth at 1,400, and progressively increase the rpm with each successive shift.

When you get to high range, you should be approaching rated horsepower before shifting.

Once you’re in top gear, bring engine rpm to your engine’s “sweet spot,” the rpm that provide the lowest brake specific fuel consumption, a figure engineers use to measure fuel efficiency.

Check your engine owner’s manual for its ideal operating speed. It may be identified as the lowest BSFC or the highest fuel economy. It varies by make and model, so look it up for your motor. That’s the speed you should cruise at.