Study: Five Tips For Fleet Fuel Efficiency

July 29, 2007
PHH Firstfleet fuel study on finding "sweet spot" to maximize fuel economy, performance

PHH FirstFleet recently announced the results of its 18-month, telematics-based fuel study of U.S. truck fleets in the grocery, manufacturing, fuel and retail markets.

The PHH FirstFleet Fuel Study, headed by applications engineer, Ezel Baltali, developed the following hypothesis: By slightly over-spec'ing engines in order to run more consistently in the "sweet spot," choosing a gear ratio low enough to suit a fleet's application and location, and enabling the correct fuel-efficient, engine-specific parameters, fuel economy will improve by 0.3 MPG (or around 5%).

The study's findings confirmed that, when combined with other variables including progressive shifting, APUs and chassis improvements, this "sweet spot" is where both fuel efficiency and performance are maximized. Additionally, the study concluded that slightly over-spec'ing engines improves fuel economy, which equates to a savings of approximately $2,000 per tractor per year (assuming 100,000 miles are driven per year).

In conjunction with the study results, PHH FirstFleet offers the following Top Five Tip List for achieving better fuel economy:

  1. Increase engine torque ratings -- Increasing torque ratings provides a simple and effective method to decrease time spent in the high output torque ranges. Driving at high output torque ratings also leads to over-revving, or RPMs higher than the engine parameters specify. Over-revving shortens the life of the engine, which sustains higher costs and lower fuel economy. On the same note, driving in a lower RPM range than the engine's specified parameters may result in driver dissatisfaction and could require increased downshifting, which indirectly causes over-revving.
  2. Decrease gear ratio -- Choosing a lower gear ratio improves fuel economy, reduces engine wear, increases speed at lower RPMs and may help reduce over-revving. In general, choose the correct rear axle gear ratio for the fleet's application and needs, but consider that while higher gear ratios may improve overall performance and provide added power in lower gears, additional power causes equipment to lose fuel economy. If improving fuel economy remains a priority, consider whether the extra performance validates the loss in fuel economy.
  3. Engine Specific Parameter Controls
    Speeding -- Above 70 MPH, a tractor's engine works to overcome aerodynamic drag. In fact, it demands over 60% of the engine's total available horsepower, which significantly increases fuel consumption. If speed is decreased to 55 MPH in the appropriate gear, the horsepower demand is reduced to only 40% and draws less fuel.
    Idling -- Idling achieves 0.0 Miles-per-gallon and uses .5 to 1 gallon of fuel per hour. Consider idle shutdown in order to save fuel while at stops.
    Progressive Shifting -- Drivers shifting quickly in lower gears prevents over-revving, which decreases fuel consumption and increases fuel economy.
  4. Spec APUs -- Auxiliary Power Units (APUs) allow drivers to run peripheral applications like air conditioning without running the engine. This decreases idling, reducing fuel consumption and improving fuel economy. Because APUs carry extra weight, the payload must decrease to meet weight limits.
  5. Chassis Improvements
    Aerodynamics -- New innovations in trailer aerodynamics, as well as roof fairings, side fairings, and bumper and side skirts, provide decreased wind resistance, which reduces required horsepower and thus fuel consumption.
    Lower Weight -- New materials allow for less weight and more potential fuel economy gains, although with decreased chassis and trailer weight, overall payloads may increase and offset the fuel economy improvements.
    Low Profile Radial or Wide Based Tires -- Research indicates that fuel economy can improve as much as 2% to 5% by using low profile and/or wide based tires and wheels. Decreased weight and lower rolling resistance are the key contributors to fuel economy improvements.

In the future, PHH FirstFleet's Fuel Study is expected to explore the relationship between maintenance, cost-per-mile and fuel efficiency. Leveraging PHH Onboard(SM) telematics and engine control module (ECM) data to correlate maintenance alerts (e.g. when cylinders misfire, battery voltage is abnormal or preventative maintenance needs to be scheduled), PHH FirstFleet expects to determine an even better cost-per-mile strategy and/or establish better maintenance procedures, which may improve MPG.

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About the Author

Brad Kenney | Chief Marketing Officer

Brad Kenney is the former Technology Editor of IndustryWeek and now serves as director of the mobile/social platforms practice at R/GA, a global marketing/advertising firm in New York City.

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