You can’t suck and blow at the same time. If you want to go up and down the road like Jack the Bear, today’s engines will deliver. If you’re thinking in terms of maxing out your RRSP at year’s end, today’s engines can help you do that, too.

But you can’t do both. What becomes of your hard-earned money is pretty much up to you-the choices you make when you spec your truck, put a little more push into your right foot, or decide to drop a gear.

You’ve probably heard all that before. And if your gearjammin’ boots are as worn as mine, words alone are insufficient to illustrate how dramatic a difference changing your driving habits can make. It takes cold, hard numbers to prove a point and take you out of your groove, especially one that’s been honed over 20 years of driving.

So I enlisted the considerable skills of Donny De Graaf, a company driver with W. A. Baker Trucking of St. Catharines, Ont. De Graaf hauls newsprint from a recycling depot in Markham, Ont., to a paper mill in Thorold, Ont. The round trip is 192 miles, and he runs empty one way. De Graaf drives a 1995 Freightliner Classic with a 70-inch flat-top bunk and an aerodynamic wing on the roof. Under the hood sits a 470-horsepower Series 60 from Detroit Diesel, coupled to an Eaton Fuller 8LL transmission running out to a 46,000-pound rear axle with 3.55 gears, sitting tall on 24.5-inch rubber. The trailer, an East Unloader walking floor, has external ribs and a soft tarp on top.

You’ll agree it’s not the most aerodynamic outfit on the road, but you’d never guess that from the numbers De Graaf turned in at the end of the day.

Trip One started with us running empty to the depot in Markham. Empty weight: 39,800 pounds. De Graaf deliberately, and against his nature, took every gear right to the pin and ran the trip at 120 km/h-pushing 1675 rpm as much as he could. We idled the truck for one hour while loading, then began the return trip.

This time, loaded to 105,640 pounds, cruising at the same speed using all the bad driving habits De Graaf could remember. The result: 35.2 Imperial gallons for an average fuel consumption of 5.45 miles per gallon.

Using 50 cents per litre as a benchmark, De Graaf’s cost per mile for fuel alone in go-faster mode was 41 cents.

Trip Two covered the same route in the same truck, but the similarity ends there. This time, De Graaf practically idled up through the gears, he kept his speed down to between 95 and 100 km/h, running the engine no faster than 1400 rpm. We hit heavy traffic on the highway, but De Graaf kept a steady pace and hardly touched the brake pedal.

In other words, he used two exactly opposite driving styles. On the way back to the mill, we grossed out at 106,520 pounds. The result: 27.6 gallons up the stacks for an average fuel consumption of 7.06 miles per gallon.

De Graaf’s fuel cost, this time out, dropped to 32 cents per mile.

As our admittedly unscientific fuel economy test indicated, driving style is the most significant factor in achieving better fuel economy. If you’re averaging 5.5 miles per gallon, fuel devours 41 cents out of every dollar you earn.

On the other hand, a truck averaging 7.0 miles per gallon is consuming only 32 cents of every dollar earned. How far would you be willing to go to put an extra 10 cents per mile in your jeans?

Results like the ones De Graaf and I recorded don’t surprise Jim Booth. The folks at Caterpillar’s engine division refer to Booth as a senior applications engineer. Actually, he’s a small-fleet owner who “test drives” all of Cat’s prototype engines under real-world conditions, in his own fleet. He’s also a recognized expert in fuel economy. According to Booth, driving for economy is as much a matter of habit as anything else.

“There’s no secret,” he says. “You just have to decide that you want better fuel economy and don’t stray from your goal.”

Booth says it’s hard getting used to the different sound the truck makes when it’s going slow, and harder still watching the scenery crawl by. And he admits it’s tough to ignore the ribbing they take for not running with the pack.

But he’ll assure you it’s worth it. You can change right now with no up-front cost, no modifications, and no special technology. Just good old-fashioned discipline. Here are five things you can do to cut your cost per mile.

1. Spec It Right

Alan Hertzog, supervisor of service training for Mack Trucks, says better fuel economy begins with the engine spec. “The most efficient engine on the market won’t deliver the fuel economy if you don’t drive it the way it was designed to be driven,” he advises.

That means doing some homework.

First, it’s important to have a thorough understanding of how you plan to use your truck so you can choose the best components for the job. That said, it’s easy to get caught up in the hype about horsepower ratings and torque output.

By themselves, the numbers say little about how an engine is designed to operate. Put them together on a performance curve and you’ve got something to work with. Performance curves indicate the engine’s performance characteristics. By interpreting that information, you can see the engine’s optimum economy range (see the “Three Lines” sidebar on page 64).

Hertzog warns against spec’ing the engine for economy, then driving the daylights out of it. “Be realistic,” he says, “and go with an engine that runs the way you’re going to drive it.”

You also have to match your engine spec to the drivetrain. That’s vital if you believe, as Jim Booth does, in a gear fast/run slow philosophy. Today’s electronic engines get their power from a high-torque, low-rpm setting, rather than the traditional low-torque/high-rpm approach. Under a gear fast/run slow ethic, geared speed is higher than the cruise speed, allowing the engine to run up and down the highway at a comfortably lazy 1400 to 1600 rpm. The result, one hopes, is better fuel economy.

But there is a limit to that train of thought. Steve Bellinger, chief assistant engineer, vehicle engineering, at Cummins Engine Co., says there’s no point in gearing a truck to run one hundred miles per hour. “You’ll get your best fuel economy if you use operating techniques that result in the lowest number of engine revolutions per mile,” Bellinger says. “But that doesn’t mean gearing the truck so high that you’ll have to run two gears back to keep it under 65 mph.”

The problem with that theory lies in the gear train. Today’s transmissions are designed to provide the lowest parasitic drag due to gear-on-gear friction in top gear. According to Bellinger, running one or two gears back causes the transmission to run through several gear meshes, in the main part of the box as well as at the back of the box, which is terribly inefficient.

“If you’re running a U.S. gross weight, keep the engine within the (published sweetspot),” he says. “With Canada’s higher gross weights, you’ll likely want to keep the engine running about 100 rpm faster at your chosen cruising speed.”

2. Manage Your Torque

Horsepower ratings have the sex appeal, but torque gets you moving. The main advantage to electronically controlled diesels is that the highest torque output happens to be in the same range as the lowest fuel consumption. It’s something you should incorporate into your driving.

An example is how to handle hills, says Dwayne Barnett of North American Truck Training Centre in Brantford, Ont. “It’s a judgment call whether or not to drop a gear right away,” Barnett says. “If you think you can pull the hill without shifting, go for it. But sometimes it’s better to drop a gear just as you begin to climb, then let torque do the rest.”

Be careful to avoid dropping below the peak torque point, though. Your performance-if not your drivetrain-will begin to fall apart pretty rapidly after that; you may even find yourself having to grab two gears instead of one on the next downshift.

3. Watch Your Gauges

One of the most underutilized fuel-saving devices on a truck today, according to Chuck Blake, staff application engineer at Detroit Diesel, is the turbo boost gauge, sometimes called the intake manifold pressure gauge. Not many trucks have these anymore, and that’s unfortunate.

Burning fuel produces exhaust, which spins the turbocharger, forcing air into the intake manifold. Excess intake manifold pressure means you could be burning more fuel than you need. Blake says there’s seldom any need to push the boost pressure any higher than 15 psi.

“If you’re getting up past that mark, you’re being too aggressive with the throttle,” he says. “Use the boost gauge as an indicator of how much throttle you need to maintain modest acceleration.”

4. Lay Off the Cruise

Blake says that in some situations, cruise control can actually cost you money. “Cruise control is a fairly aggressive throttling mechanism. It’s designed to keep the truck at a steady speed, which the computer may decide requires a full-throttle application,” he says. “A driver can usually out-do cruise control for fuel economy by simply letting up on the pedal a bit when climbing a rolling hill. Do you really need to hit the top at the preset speed?”

Blake says it’s also important to conserve momentum whenever possible by minimizing the use of the brakes. Rolling to a stop rather than hammering in and slamming on the brakes saves money on both ends.

If all this talk of running at1200 rpm has you concerned, don’t be. The old theories about “lugging” an engine just don’t apply anymore. Lugging means you’re pouring more fuel into the cylinder than the engine can burn efficiently, hence, the black smoke and high exhaust temperature. Today, engines are designed to operate effectively in the 1000 to 1200-rpm range. Get down there, stay there, and let ‘er pull. You can also throw that pyrometer out the window; it’s next to impossible to overheat an engine under normal operating conditions.

Diesel engines continue to change at a rapid pace, and old driving habits die hard. But when the difference between 5 and 7 miles per gallon, at current Canadian diesel prices, is $16,185 per year, how many more bones does an old dog need to learn a few new tricks?

*** SIDEBAR: 5 tips to help keep you in the green

Donny De Graaf’s four-year-old Freightliner Classic, 470-horse Detroit engine, and tarped-over trailer (above) hardly fit the profile of a slippery fuel-sipper. Yet Donny has found find common-sense ways to drive his 105,640-pound rig all the way to the bank:

1. Forget “Miles Per Gallon.” Learn to equate fuel consumption with cost per mile. Miles per gallon is a fairly intangible number, while cents-per-mile has a real value.

2. Spec your truck, then truck your spec. Consult the charts before you build the truck, then drive it the way you designed it to be driven.

3. Easy does it. Use the turbo boost gauge as an acceleration meter. Try to keep the intake manifold pressure to a minimum. Anything over 15 psi means you’re probably in too much of a hurry.

4. Maintain a steady speed. Let traffic flow around you and maintain adequate space so as to avoid having to brake or accelerate to keep up. Get used to driving slower than everyone else.

5. Progressive shifting. This is probably the most overstated and underutilized fuel-saving theory known to mankind. You can easily go through the bottom of the box without ever exceeding 900 rpm. Shift at the absolute minimum rpm for each gear.

*** SIDEBAR: Three lines that will make or break you

How does a graph on a piece of paper translate into operating expectations and operating costs? The performance curves are easy to understand once you know what you’re looking at.

The top line (green) is the torque curve. It indicates the engine’s torque output at a given rpm. The middle line (red) is the horsepower curve. It indicates the horsepower the engine produces at a given rpm.

The bottom line (blue) is the fuel consumption curve. Known technically as the Brake Specific Fuel Consumption (BSFC) curve, it’s not directly equivalent to miles per gallon, but as a general rule, the lower the BSFC, the better the fuel economy should be.

The graph to the right shows that this engine produces its peak torque of 1650 pound-feet anywhere between 1100 and 1200 rpm. The horsepower curve indicates how the horsepower output increases as the engine speed increases, to a peak of 465 horsepower at 1700 rpm. The fuel curve indicates that peak fuel economy exists at 1400 rpm. There, the engine is producing approximately 425 horsepower and 1575 pound-feet of torque. The “sweet spot” for this engine would be between 1300 and 1500 rpm.

Use the performance curves when spec’ing your drivetrain to achieve peak economy at your desired cruising speed.

Note that this graph is based on one particular engine (Volvo’s VE D12C) . Other engines are engineered to produce different performance curves for different applications, and they can vary considerably.