Vehicle Parts and Equipment to Conserve Fuel
Only about 12%–30% of the energy put into a traditional combustion engine goes toward its propulsion on the road—especially in modern vehicles. Most of the energy is lost to engine and driveline inefficiencies, like exhaust heat, or is used to power accessories like air conditioning. Vehicle fleet managers and drivers can conserve fuel and maximize their operational efficiency by driving efficiently and outfitting their vehicles with commercially available equipment designed to save fuel. Implementing fuel-efficient strategies, systems, and programs for some or all vehicles can help fleets monitor and better manage their vehicles, vehicle-related costs, and carbon footprint. These strategies are cost-efficient and do not require extended vehicle downtime.
Low Rolling Resistance Tires
Rolling resistance is the energy lost from drag and friction of a tire rolling over a surface. The phenomenon is complex, and nearly all operating conditions can affect the final outcome. Conventionally fueled passenger vehicles use about 4%–7% of their fuel just to overcome tire rolling resistance. All-electric passenger vehicles can use approximately 25% of their energy for this purpose. For heavy trucks, this quantity can be as high as 30%–33%. A 10% reduction in rolling resistance would improve fuel economy approximately 3% for light- and heavy-duty vehicles. Installing low rolling resistance tires can help fleets reduce fuel costs. It's also important to ensure proper tire inflation.
New cars are generally equipped with low rolling resistance tires that offer better fuel economy. This helps the auto manufacturer meet its Corporate Average Fuel Economy (CAFE) and greenhouse gas emission requirements. However, no statutory requirements are currently placed on replacement tires. Therefore, if you want to purchase fuel-efficient replacement tires, you must research which replacement tires that are appropriate for your vehicle have low rolling resistance.
Signed into law on December 4, 2015, the Fixing America’s Surface Transportation (FAST) Act requires the U.S. Department of Transportation to develop passenger vehicle tire fuel efficiency standards. Some exemptions apply. For more information about the FAST Act standards, refer to Public Law 114-94.
In 2022, the U.S. Environmental Protection Agency (EPA) proposed new greenhouse gas emission standards for heavy-duty vehicles, which are based on several vehicle performance improvements, including improvements to tire rolling resistance. For more information, see the proposed rule, "Control of Air Pollution from New Motor Vehicles: Heavy-Duty Engine and Vehicle Standards".
Tires and fuel represent significant costs in a fleet’s portfolio. In Class 8 trucks, approximately one-quarter of fuel efficiency comes from the rolling resistance of the tire, making the opportunity for cost-effective energy savings substantial. According to a 2020 North American Council for Freight Efficiency (NACFE) report, the use of low rolling resistance tires, in either a dual or a wide-base configuration, is a good investment for managing fuel economy, as the fuel savings may pay for the additional cost of the tires. In addition, advancements in tire tread life and traction will reduce the frequency of low rolling resistance tire replacement. Fleet managers can use the total cost of ownership calculator referenced in NACFE’s report to assess their own duty cycles, business models, and other considerations to determine which tires are right for their fleet. Fleet managers can work with their preferred tire company to identify suitable tires for their vehicles. EPA's SmartWay program also provides a list of verified low rolling resistance tires for medium- and heavy-duty applications.
In Class 8 trucks, replacing traditional dual tires with one wide-base (also called super-single or single-wide) tire can save fuel by reducing vehicle weight and rolling resistance, which means the engine doesn't need to work as hard. A wide-base tire is not quite as wide as the sum of the two tires, so there is a slight aerodynamic benefit as well, further improving vehicle efficiency. Using wide-base tires can improve fuel efficiency by approximately 1%–2%. For example, Mesilla Valley Transportation improved their fuel efficiency by equipping vehicles with wide- base tires and low-viscosity synthetic lubricants to reduce drag and improve vehicle performance.
Aerodynamic Equipment and Vehicle Design
By reducing the drag, or resistance, imposed on a vehicle traveling at high speeds, aerodynamic equipment eases the load on the engine and improves the fuel economy of a vehicle. Airfoils, trailer gap reducers, side skirts, under trailer devices, aerodynamic splash guards, and tails are examples of aerodynamic equipment that fleets can install on trucks to reduce driveline losses. Airfoils direct air over the cab, trailer gap reducers lessen air turbulence by minimizing the space between the cab and the trailer, and side skirts limit the air that circulates under the trailer. Under trailer devices channel air to reduce turbulence, aerodynamic splash guards reduce drag compared to traditional splash boards, and tails reduce the turbulent airstreams dragging behind the trailer. EPA's SmartWay program provides lists of verified aerodynamic devices.
Many light- and heavy-duty vehicles (HDVs) that manufacturers are developing have streamlined vehicle designs that reduce drag. More information on aerodynamic tractor and trailer equipment for HDVs can be found in NACFE's Confidence Reports.
Idle Reduction Equipment
Idle reduction technologies reduce the amount of time an engine idles unnecessarily. Auxiliary power units, bunk heaters, batteries, and other idle reduction equipment can help reduce idling and save fuel. EPA's SmartWay program provides lists of verified idling reduction technologies for trucks and school buses. A number of tools developed by Argonne National Laboratory, such as the Idle Reduction Savings Calculator and the Alternative Fuel Life-Cycle Environmental and Economic Transportation (AFLEET) Tool, help fleet managers and drivers calculate the time they idle and the environmental benefits of idle reduction equipment, allowing them to identify the most cost-effective ways to improve their idling profile and potential savings.
Long-haul fleets can use complementary equipment in some truck stop parking spaces on or with their vehicles to improve efficiency and conserve fuel. Fleets can also take advantage of electrified parking spaces, also known as truck stop electrification, which provide power to necessary systems such as heating, air conditioning, or appliances without idling the engine (see example case studies for fleets in New Jersey and St. Louis, Missouri). Many of these investments have short payback periods.
Fuel-Tracking Devices and Telematics Systems
Data collection devices installed in vehicles can track fuel economy, maintenance schedules, and fleet performance to help fleets monitor fuel consumption, improve fuel economy, and increase asset utilization. For example, the Public Service Company of New Mexico’s fleet installed a telematics system to monitor fleet performance, track driver behavior, and inform driver training. With these devices, the fleet improved their average fuel economy by 15%.
Electronic logging devices automatically record hours-of-service and driving time data and are required on certain commercial buses and trucks. Through the use of global positioning systems and communication technologies, telematics provides fleet managers with data about vehicle location, vehicle use and miles driven, idle time, fuel economy, driver behavior, and engine maintenance requirements. Many of these telematics systems are paired with powerful software packages or driver training programs to help track vehicle activity and manage fuel consumption. Some devices give drivers real-time fuel economy feedback, which has proven effective in reducing fuel use. Other devices can also provide data to help fleets make informed decisions about maintenance and vehicle replacement.
To determine what telematics systems data to focus on, a fleet should identify its top priorities, such as idle reduction or efficient routing. The fleet can then work with a telematics provider to determine key performance indicators and extract the most important data. This planning will help the fleet use the data to deliver efficiency improvements. For example, in a telematics deployment study with the Marine Corps fleet, researchers at the National Renewable Energy Laboratory (NREL) calculated the total savings from telematics for various light-duty vehicles and shuttle buses. When used in the Marine Corps fleet, telematics had the potential to help fleet managers save more than $2,000 per vehicle each year. Also, learn how NREL used telematics to help five fleets explore the benefits of obtaining electric vehicles.
Speed Control Modules
Fleet managers can install electronic speed control modules to prevent vehicles from traveling faster than a specific speed, which can conserve fuel and promote safer driving practices. For light-duty vehicles, every 5 miles per hour (mph) over 50 mph is equivalent to paying an additional $0.30 per gallon of gasoline (based on the price of gas at $4.32 per gallon). For example, Brown Trucking, a short-haul carrier operating in the Southeast, improved its fuel economy from 5.7 miles per gallon to 6.4 miles per gallon through technology and driver training.