Companies spend an enormous amount of money fueling vehicles; as of May 2006, diesel costs were up 34 percent over the same time last year. While ordinary consumers may have good reason to shrug their shoulders and exhale at the fact their fuel-money-saving options are limited, this isn’t the case for fleets. Even a small improvement in fuel efficiency, when multiplied by miles and trucks, makes a big difference.

Using Telematics to Study Truck Fleets
Truck fleet managers already know several factors affecting fuel efficiency — idling time, road speed, terrain, and application — that they’ve been working to mitigate. Some of these factors are simply uncontrollable. But a privately sponsored multi-fleet study is uncovering other ways to cut fuel expense. PHH FirstFleet is conducting a truck fleet fuel consumption study, innovative research that uses telematics technology to examine fuel economy in heavy-duty trucks.

While PHH FirstFleet began the study only looking at Class 8 trucks to obtain fuel economy solutions applicable to a wider range of fleets, the company later decided to study medium-duty Class 3-7 trucks as well. Similar results are expected between Class 8 and medium-duty trucks, although medium-duties differ, for example, in that they don’t have the same variety of gear ratios as a Class 8. Such differences may slightly affect fuel economy.

The study, six months into its 18- month life span, is being conducted across the United States in various terrains and climates. The information reflects normal operating conditions. Companies agreed to work with PHH FirstFleet and have the PHH Onboard Telematics devices installed in their medium- and heavy-duty trucks. Each truck’s individual device periodically sends data to a database at the PHH FirstFleet office in Fort Lauderdale, Fla.

Engine Specing and Gear Ratios
The study’s initial findings show twomain factors companies can control or modify to increase fuel economy: engines specs and gear ratios.

“Overspecing your engine to optimize output torque has shown improvement in fuel economy,” says Ezel “C.J.” Baltali, PHH FirstFleet’s fleet services application engineer. “Gear ratios are also important because you always want to make sure you have the right gear ratio ratings for your specific applications.” A fleet can’t change the terrain it drives on, but the engine can be spec’ed and gear ratio selected to best handle the environment and payload.

At this point in the study these findings have been consistent, but remain generalizations. However, Baltali reports they’ve found that horsepower roughly in the 455 range has proven a maximization point for fuel efficiency for Class 8 trucks, and that gear ratios over three don’t provide as high a fuel economy as those under three.

Two different fleets, one from Northern California and the other from the Northeastern U.S., were compared in how many miles per gallon they achieved using different gear ratio settings. Both fleets had a torque of 1,550 lb./ft. @ 1,200 rpm, roughly equal horsepower (455 for the Northern California fleet and 435/475 for the Northeast fleet) and ran on the same kind of terrain. California’s gear ratio was 2.79, while the Northeast’s was 3.90. The average mpg for the California fleet was 6.5; Northeast’s was 5.0.

“What you want to do is keep the engine out of the high torque range as much as possible,” says Hal Booth, senior vice president, PHH FirstFleet. “And if the engine is underspec’ed or the gear ratio is wrong, and you’re running on high torque, you’re using a heck of a lot of fuel.”

Booth says that keeping a low torque range while overspecing horsepower and rpm in order to increase fuel economy will impact maintenance expenses, slightly raising acquisition costs, but he says this is offset by the resulting higher resale value.

Creating a Control Group to Analyze Details
PHH FirstFleet has created a fleet control group whose settings will remain unchanged so, when compared to fleets that will receive tweaks in engine and gear settings, a more detailed analysis of engine parameters and gear ratios can be made.

Whether either overspecing the engine or changing gear ratios individually makes a difference in fuel economy is not yet known, but PHH FirstFleet is on its way to finding out. The company’s goal is to help customers achieve a 0.3 miles per gallon improvement in overall fuel economy. Doesn’t sound like much? That’s $2,000 per year per Class 8 truck, or $200,000 a year for a fleet of 100.

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