One of the big challenges for fleet owners, especially in site development and other construction activity, is fuel economy. While fleet managers can’t control fuel prices, choices made when spec’ing and driving medium-duty and heavy-duty trucks and off-road equipment can make a difference on how much mileage - or work - the fuel delivers.

By Joseph Lynn Tilton

Weight Reduction Helps Boost Mileage
Overall Fuel Economy
Lighten the Body
Tire Cure Helps
End-Users' Views
Driver Comfort = Driver Rentention
What Goes Around...

The first step in spec’ing for fuel economy is to determine the right combination of engine horsepower, transmission, and axle configuration for the truck’s application. If the truck has too much—or too little—power to get the job done right, it will waste fuel and ultimately waste money.

"In every application, from hauling dirt to local delivery, fuel consumption is a significant factor in determining a fleet’s profitability," says Dan Ustian, president of International’s Engine and Foundry Group.

He also points out that cooling fans are another culprit of reduced fuel efficiency because they can take up to 30 hp from the engines at high speed, thus cutting mileage on the on-road portion of a project. For such, an on/off fan drive, which only runs when the engine needs to be cooled, can improve fuel economy by 5-10%. Torque also makes a difference. In most cases, a high-torque engine is more fuel efficient because it can be operated at a lower speed without a loss of horsepower. This can result in up to an 8% savings in fuel economy.

Weight Reduction Helps Boost Mileage

"When spec’ing in the interest of fuel economy, make use of lightweight components," declares Stephen Ginter, vocational product manager for Mack Trucks Inc. of Allentown, PA. Also, let technology help you obtain maximum operating efficiency by specifying the latest in electronic engine and vehicle control systems.

Ginter then gives the example of Mack’s 12-lit. engine. "It’s 500-700 pounds lighter than the 12.7- to 14.5-liter engines, yet provides the 300-460 horsepower, with the necessary torque, to move that machine wherever it’s got to go."

He adds that the Mack E-Tech with V-MAC III (Vehicle Management and Control) electronic technology can offer an additional 10% fuel savings over a mechanical engine. "Electronics are very user-friendly, particularly when a dash-mounted vehicle information profiler allows direct contact between the driver and the computer controls. Electronics help fleet managers keep track of each engine’s performance by recording road speed, how many times the clutch is pushed in, PTO [power take-off] activity, and so forth."

Ginter, who has been in the industry 21 years, continues, "Information helps the driver improve his driving skills to maximize fuel economy. For trucks on construction sites, the gallons-per-hour consumption is recorded. The Vehicle Management and Control system not only helps drivers economically operate their trucks, but fleet managers are able to program characteristics of operation. For example, there are many customer-programmable features, such as top road speed, idle shut down, and cruise-control settings, to name a few."

He continues, "The electronic engine has the quickest throttle response of all engines. The electronic throttle can be set to jump to the rpm wanted for warming up, then be eased by the driver when the desired temperature is reached. Multiple PTO controls can be programmed, which can really help that vehicle operate most economically for the specific task at hand."

Even better, an electronic engine such as Mack produces includes operational histograms. "These allow the driver or fleet manager to extract the data wanted. For example, he might want to know how often the vehicle is operating at its most fuel-efficient mode. The histogram records when the driver is shifting the truck and taking advantage of the most powerful part of the torque curve. After all, if an engine develops its peak torque at about 1,100 rpm, and recommended cruising rpm is 1,500, you get the best fuel economy between 1,100 and 1,500 rpm. The driver can lug our MaxiCruise engine down to 1,100 rpm before downshifting. If the driver shifts too soon, then he is shifting out of the best torque or the ‘sweet spot’ for power and fuel economy." Ginter sees this as a chance for positive driver feedback. "The fleet manger can look at the driver profile, at the way the vehicle is being driven, and tell the driver, ‘Looks like you’re doing fantastic; you’re getting the best possible fuel economy.’" He concludes, "If you’re going to improve fuel economy, then you need to be able to measure that improvement."

Overall Fuel Economy

"When it comes to economy, there are two ends of the spectrum," explains Scott Pearson, general marketing manager for Peterbilt Motors Company in Denton, TX. Electronic fuel controls help engines work at their highest efficiency, he points out. "When spec’ing equipment, whether for refuse, construction, hauling or combined on/off highway use, consider grade-ability and start-ability.

"Look closely at the job application. For example, we have vehicle configurations with lightweight components and increased weight ratings, which allow more payload. That way, you move the same payload with one truck instead of two. The net result is fuel economy. Drivers also are responsible for fuel economy. They need to watch idle time. You can really idle away your money."

And drivers need to understand the relationship between automated transmissions and electronic engines. "Automated transmissions force vehicles to shift at optimum rpm and maintain that rpm range in the sweet spot of the engine. Drivers need to avoid over-rpm prior to shifting," Pearson advises.

Another aid is today’s Central Tire Inflation System, which allows the driver to adjust tire pressure from inside the truck to increase the tire’s footprint in soft or sandy soil conditions. "This enables the truck to maintain optimum traction by lowering the tire pressure on the run, then immediately raising the pressure to the manufacturer’s specs when the truck reaches solid ground," Pearson describes.

The E-Tech engine has brake-specific fuel consumption at or below 0.300 lb./hp-hr.

"When spec’ing an automatic transmission for on/off highway, the big thing you’ve got to watch is your ratio coverage for wheel slip," adds Mitch Murray, manager of tactical marketing for Allison Transmission in Indianapolis, IN. "The thing you’re really spec’ing for is tractive effort in construction."

He then discussed his company’s Computerized Application Analysis system and how it helps distributors make sure their customers are spec’ing for proper tractive efforts when they encounter soft conditions. "With an automatic, you don’t want to mash on the accelerator when you are axle deep with the wheels frozen in mud. You want to be certain you have enough power to spin wheels or you’ll burn up the transmission. If you’re mashing the pedal and wheels are not turning, every bit of power is going into heat. That’s why ratio coverage and power are the two critical elements that help your vehicle negotiate all kinds of terrain."

At the same time, the person doing the spec’ing needs to keep the top end in mind. "You want to be able to keep up with the traffic when you’re on the freeway so people aren’t cussing you out. This is where overdrive transmissions really help," Murray remarks.

Best of all, automatic transmissions are much more durable than in days of yore. Murray notes, "Manufacturers size transmissions to handle an engine’s standard torque, yet a converter can double that torque. So we size the gears and bearings in your prospective transmission to handle that level of torque."

He then notes that his firm’s automatic transmissions carry double the warranty versus the competition, giving users two years instead of one. "We also have extended transmission coverage for construction that we will be introducing in July. A real benefit with automatics, though, is that less skilled drivers can use the equipment in difficult terrain a lot better. They don’t get stuck as much. That’s because when they hit the soft stuff, they keep going, they don’t have to downshift."

Lighten the Body

Another challenge is maximizing load capacity while minimizing total weight. According to Ron Gerding, products manager for Heil Company in Tishomingo, MS, "We have the lightest dump body and hoist system in the industry. On the return trip, we’re lighter than anybody else, which conserves fuel. Also, lighter components make it possible for trucks to haul an extra 100-1,000 pounds."

The interlaced subframe provides extra strength and gives more floor support. Gerding admits this is not new technology. "I’ve been here 26 years, and they were using that technology when I arrived." But the work is to get the chassis’ strength up and its weight down.

"Aerodynamics, especially in operations including highway travel, is another consideration. And even when it isn’t, an aerodynamic body is more appealing." After all, who wants to run a truck that looks like everything else on the road? He adds, "End users can spec out their own dump body on-line at www.duraclass.com."

Hydraulic-lift-system improvements have also played a role in fuel economy. That, says Gerding, is because operating pressures have doubled to 2,500 psi, making it possible to go to a lighter cylinder, to a 6-in., three-stage telescoping rig instead of the heavier 8-in. version. But what about durability? "One of our end users said the best thing about our three-year warranty is that he doesn’t need to use it. It is best to have a good preventive-maintenance program, follow the lube chart and keep the mechanism greased, and follow oil-change recommendations for hydraulic oil."

Another aid with today’s equipment, such as that manufactured by Heil, is ergonomically strong dump bodies. "The Durapave, on our asphalt option, is designed so that paving material, for example, is dumped directly into the hopper. When the driver pulls away, there’s no asphalt on the ground. The driver doesn’t have to get out and clean off the asphalt apron—leaving the truck running and consuming fuel," Gerding explains.

Tire Care Helps

"Perhaps the best tire-related fuel-conservation effort that construction fleets can make is to move to radial tires," declares Don Schauer, manager of fleet communication for Bandag Inc. in Muscatine, OH. "When it comes to tires, everything is a compromise. If you maximize one feature benefit, you will negatively impact another. In our experience, while fuel conservation is important to everyone—especially at the current pump prices—when it comes to the bottom line, a construction fleet must be more concerned about other features and benefits its tires deliver."

Schauer’s benefit list includes traction, cut and chip resistance, and durability on construction sites. "Those can provide a construction fleet with measurable cost savings."

A close-up of the TufTrac vocational suspension in action.

End Users’ View

"I’ve used radial tires as long as I’ve been in business," states Denton Williams, president and founder of Blue Max Trucking in Charlotte, NC. "You can’t go off-road with bias because you’ll spend too much time on maintenance, on handling tire punctures, and so forth." Blue Max began in 1984 as a one-truck operation. Williams now has a fleet of 145 trucks operating in a 75-mi. radius.

Though they’re all dump trucks, a quick glance at the fleet shows that Williams does his spec’ing carefully. His fleet consists mainly of Mack, Peterbilt, and Sterling, with Allison transmissions and Michelin and Bridgestone tires rounding out his choices in his quest for operating efficiency in an environment that’s 90% highway and 10% off-road.

As with other operators, the ongoing challenge is finding excellent drivers. Adds Williams, "A lot of people can drive a truck, but they can’t change gears. So automatics save a lot of shop time as well as fuel. To me, dump trucks are harder to drive than to run over the road. So many more hazards—overhead wires, people walking behind you, lots of chances for an accident—so you must be on your toes. We have to teach some drivers how to drive a dump without having to worry about changing gears or rolling out of spreaders, letting the clutch slip, et cetera. Automatic transmissions make it easier to do a safe job."

Williams and his shop foreman, Dwayne Hammill, are real sticklers on preventive maintenance as well as safety. "We have regular service intervals, and all trucks keep a clean appearance. This is not a normal dump-truck fleet; the machines are kept clean at all times." The fleet also is on a five-year cycle, and Williams gets at least 375,000 mi. out of a vehicle in that time.

"Sure, technology helps you do a better job, but it’s still up to the driver. You’ve got to have capable drivers." Williams reports that they normally don’t have to advertise for help. He notes that his fleet is kept busy from April until Christmas. "Then we’re pretty much shut down in January, February, and March. If times get especially slow, then we have to lay off."

Driver Comfort = Driver Retention

Not only do the right cabs provide fuel economy for the on-road part of the vehicle’s operation, but they also help in driver retention in an industry where turnover continues to be a challenge. Kevin Martin, vocational sales manager with Sterling Truck Corporation in Willoughby, OH, points out, "Ironically, while companies put a lot of effort into wages and benefits, too often they don’t give enough attention to driver comfort. That’s where a properly spec’d cab can make a difference. Our goal is to produce an extremely comfortable cab for even the largest driver, as well as to provide excellent visibility, which reduces fatigue. Cab comfort helps drivers feel at home. They’re more productive, especially at the end of the day."

Martin highlights the need to pay attention to suspension. "Users need high articulation for maximum ground clearance at construction sites. High articulation enables dump, mixer, or asphalt trucks to maneuver freely in all off-road conditions. Loss of traction becomes less of a problem, which saves time, which saves fuel."

Jim McNamara, manager of public relations for Sterling, adds, "All these improvements to trucks reduce costs and increase efficiency. All features have a positive effect on the bottom line. The driver is more productive at the end of the day and gets more work done. A cab with wide steps and handles on both sides is easier to get in and out of, and it reduces slips and falls, which in turn reduces injuries and workers’ comp expenses."

Notes Martin, "Driver retention is one of the biggest issues in the industry. When the hours and benefits are equal, the quality of the drive can make a difference. Placement and lighting of gauges contribute to a driver-friendly environment. Drivers want comfort. Besides, they take better care of trucks they like."

What Goes Around…

Tires are another essential element when spec’ing a vehicle. "Over rough terrain, pressure is crucial," says Roger Stansbie, national field engineering manager for the commercial division of Continental General Tire in Charlotte, NC. Looking back over his 35 years in the industry, Stansbie comments, "Off-road pressure is not as defined as over-the-road, but if that tire is overdeflected, then it’s going to absorb energy that comes from one source: the fuel tank."

Correct tread design is another important element. "If you don’t have a good grip, then you have slippage, which wastes time and energy. Tires do warm up, and they can get real hot, especially in rough terrain. The goal of the tire manufacturer is to reduce rolling resistance, which reduces heat buildup. Most off-the-road people say the main thing is to get the job done in the most economical time available. They’re working to a contracted price, and the less time it takes to do a job, the less fuel that will be used.

"Moving from bias to radial is necessary, especially when on-road hauling is part of an operation," Stansbie emphasizes, "such as when pulling out of a mine or highway site and dumping heavy loads even just 2-3 miles away. As road trips get longer and longer, radials are the only thing that will survive the long haul."

Sidewall damage is another challenge. "The main thing in any application is to keep the site clean of debris that can impact the tires. Cleaning the site is a constant problem, one that needs a lot of vigilance."

Ditto tire pressure. "Inflation should always be within 10% of what’s recommended for the load being carried on that tire," Stansbie emphasizes. "You want to avoid overinflation as well as underinflation. The biggest damage is brought by underinflation because you compromise the casing. With overinflation, tread wear is more of a concern than tire breakdown." Further, money spent on inordinate tire repairs could more easily pay for fuel.

Goodyear engineers also emphasize the need to choose the right tire. Radial tires offer many advantages, including longevity, traction and flotation, fuel savings, and driver comfort. "One of the biggest challenges is getting people to see the advantages of radial tires," agrees Robert Potts, application engineer for off-road tires. "Almost invariably there is an initial resistance to radials by operators. After just a very short experience, however, they prefer the radial and want to stay with it. With radials, they’re less beaten and jostled about."

For the owner, the advantage is 25-50% greater tread life than with bias. Further, Potts notes, "The radial footprint is laid down like a bulldozer track, while the bias rolls along the ground like a hoop. But radials are more sensitive to inflation, and proper air pressure must be maintained. While inflation is different for each machine, Goodyear advises that users follow the vehicle manufacturer’s recommendation or that of their tire supplier."

Fellow engineer Gene Lunieski adds, "The steel belt in the radial offers puncture resistance, while lab reports say radials have a 25% improved impact resistance." Both engineers note that their company makes both types of tires and that there is a place for the bias tire. Those places include machines in little use where initial cost is most important and stability is a strong criteria, though the instability of the radial is more of a perception than a reality.

Gregg Trexler, team leader for Goodyear’s Off-Road Tire Advanced Design Group, comments, "Essentially, fuel economy is one of the advantages of radial construction. On haul roads, one can achieve 5-7% fuel savings when traveling between 20 and 30 miles per hour, while off-road radial fuel savings is more like 3-5%." The savings comes mainly from less rolling resistance and less tire slip. Trexler adds, "Radials improve tractive efficiency and increase flotation, which translates into increased fuel efficiency." The Goodyear engineers note that motor-grader radial tires come in two basic types of tread design: an aggressive traction bar and an all-season tread design basically for working in snow removal and with loose soils.

Lunieski adds, "In many cases, going to all-season radial tires eliminates the need for chains. By going from bias to radials with a longer footprint, you get better traction, while the all-season eliminates the need for chains in many cases. This might save having to chain up during a bad environment—with the engine running while the operator gets the equipment ready for the task at hand. Our all-season has been designed so the chains ride on top of the lug elements rather than fall between where their effectiveness is greatly reduced." So whether the vehicle is used for landscaping, snow removal, road building, or in connection with a landfill operation, spec’ing the right components can open the door of opportunity for greater profitability, growth, and efficiency.

GX
July/August 2000