Quick tips to keep fuel consumption down and optimize operating efficiency.
By Allison Kirbo

A recent report from the American Transportation Research Institute found that fuel costs accounted for 28 percent of total fleet operating costs in 2022, a 6 percent increase from the year prior. Diesel fuel prices have been declining over the last several months, but are still high, currently averaging $4.281 per gallon nationwide, and the U.S. Energy Information Administration only expects prices to gradually decrease into the first half of 2024.

When you consider the fact that filling up a semi-truck requires anywhere from 120 to 300 gallons of fuel depending on how many tanks it is equipped with, it is no wonder that controlling fuel consumption and optimizing efficiency are currently one of the top priorities for truck and fleet owners.

#1: Reduce Speeds
Did you know that every 1 mph increase in speed over 65 mph equals a 0.14 mpg decrease in fuel economy? Driving faster causes your truck to burn fuel quicker, leading to more frequent stops at the fueling station and more money spent on diesel than necessary.

According to the American Trucking Association (ATA), a truck driving at 75 mph on the highway will consume 27 percent more fuel than a truck driving at 65 mph. To put this into perspective, imagine a truck that gets 6.6 mpg and drives 1,000 miles at 65 mph. During the trip, the truck would have burned approximately 152 gallons of diesel fuel. If the driver were to make the same trip at 75 mph, and we assume fuel efficiency decreased by 1.4 mpg due to the 10 mph increase in speed, the truck would burn 40 more gallons of fuel to travel the same distance.

At current diesel fuel prices, that is $170 the driver would not have had to spend if they had reduced their speed. The ATA estimates that capping truck speeds to 65 mph would net the trucking industry $2.8 billion in savings on fuel over 10 years.

#2: Use Cruise Control
Just like driving at lower speeds burns less fuel, driving at a consistent speed can bring even further improvements to fuel efficiency. When available, cruise control can help you maintain a consistent speed while also limiting unnecessary acceleration and deceleration, which are some of the most wasteful cycles for a truck’s engine. Studies have shown that cruise control can provide up to a 6 percent decrease in fuel consumption throughout a trip.

#3: Find Your Engine’s RPM “Sweet Spot”
Every truck has an optimal operating range when it comes to revolutions per minute (RPM), and this will vary based on the truck and engine model. Engines are designed to run at high torque (the rotational force of an engine) and low RPMs. The lower the RPM, the less fuel is consumed.

The most efficient RPM at which your engine can run is called the “sweet spot,” and typically ranges from 1,250 to 1,350 RPM. Keeping your engine at its RPM “sweet spot” requires driving at a consistent and slower speed. The manufacturer of your engine can provide its peak operating horsepower and torque to help you identify your RPM “sweet spot.” It is important to note that you never want your engine to exceed 1,500 RPM.

#4: Pay Attention to Your Tires
Your tires can affect your truck’s fuel efficiency in more ways than one. For starters, your engine has to work harder to move the truck forward when your tires are underinflated. The National Highway Traffic Safety Administration (NHTSA) reports that you can expect a 0.2 percent reduction in fuel economy for every 1 psi that your tires are under the recommended pressure. On the flip side, keeping your tires properly inflated has been found to provide savings of up to $0.11 per gallon. While this does not sound like huge savings, it can quickly add up.

The rolling resistance of your tires also has a large impact on fuel efficiency. Rolling resistance is the energy required to keep tires moving at a consistent speed. The more energy required to keep the tires in motion, the more fuel is burned. Low-rolling resistance tires typically have thinner sidewalls, shallower tread patterns, and special rubber compounds that make them lighter and produce less rolling resistance and friction. The U.S. Department of Energy (DOE) has found that a 10 percent reduction in rolling resistance can improve fuel efficiency by approximately 3 percent.

You should also have the alignment of your front and rear axles checked regularly, as misalignment can significantly increase rolling resistance. In fact, misaligned axles can increase fuel consumption by up to 3 percent. If all trailer axles are also misaligned, you can see up to a 15 percent increase in fuel consumption.

#5: Minimize Idling Time
Letting your truck idle temporarily while driving a route is unavoidable, but keeping idling time to a minimum can provide significant fuel savings. A 2015 report from the DOE found that a semi-truck burns 0.8 gallons of fuel each hour it sits idling and a long-haul truck will idle approximately 1,800 hours per year. This means that just letting the truck sit with the engine running would burn 1,440 gallons or $6,1672 worth of diesel fuel over the course of one year. At current fuel prices, reducing idling time by just 10 percent annually could save drivers more than $600 on diesel fuel.

The Argonne National Laboratory estimates that truck idling in the U.S. consumes up to 1 billion gallons of fuel annually, costing the trucking industry an estimated $3 billion. To reduce idling time, fleets and owner-operators can invest in Auxiliary Power Units (APUs) that provide electricity to the truck’s cab without keeping the truck in idle mode. APUs can either run on diesel or an electric battery; however, diesel-powered models burn significantly less fuel than the truck’s engine. An Automatic Engine Start/Stop (AESS) system can also reduce idling by automatically starting and stopping the engine to maintain cab temperatures so that the engine does not have to consistently run overnight.


#6: Focus on Aerodynamics
Aerodynamic drag is another culprit that can decrease fuel efficiency and lead to higher fuel costs. However, several small modifications can be made to make a truck more aerodynamic, reduce its drag and improve fuel economy. When driving at speeds more than 50 mph, just a 2 percent reduction in aerodynamic drag will result in a 1 percent increase in fuel efficiency.

Removing unnecessary external accessories, such as extra lights, bull bars, top bars, and air horns can also reduce drag and reduce fuel consumption. Below are just some of the modifications that can be made to reduce aerodynamic drag:
Side Fairings/Cab Extenders—Attached to the side of the truck cabin to direct airflow away from the gap between the tractor and trailer.
• Fuel Tank Fairings—Added to side-mounted fuel tanks to allow air to flow past them.
• Roof Fairings and Spoilers—Placed on the roof of the cab to direct wind across the roof and up and over the trailer.
• Wheel Covers—Cover all of the air-trapping gaps in truck tires, allowing air to flow past them.
• Side Skirts—Placed underneath the trailer between the trailer’s axles to redirect airflow and eliminate drag from the undercarriage.
• Trailer Tails (Boat Tails) —Added to the end of the trailer to reduce turbulence at the rear and prevent the formation of a low-pressure vacuum.

#7: Use Technology to Optimize Routes
It is no secret that heavy traffic, poor road conditions, and hilly terrain can cause your truck to burn more fuel. However, determining the most efficient and effective routes for drivers to follow can reduce idling and decrease consumption. This involves taking distance, traffic conditions, road restrictions, weight limits, and delivery schedules into consideration to find routes that will get cargo where it needs to go as quickly and efficiently as possible.

Fleet management systems and telematics software can help with this by optimizing driver operations to ensure they are traveling the most efficient routes and avoiding traffic congestion or weather issues in real time. Telematics systems can also provide automated alerts when drivers are speeding or idling for too long to help decrease behaviors that lead to increased fuel consumption and reduced fuel economy.

#8: Keep Up with Preventative Maintenance
While staying on top of preventive maintenance services for your vehicle can provide many benefits to keep you on the road longer, it can also help you prevent issues that may cause higher-than-normal fuel consumption. Brake drag, seized brakes, clogged air and fuel filters, pressure leakages, and fuel leaks can all cause your truck to waste fuel and decrease your fuel efficiency. A certified technician should check for these issues on a regular basis and make sure all components are in peak condition.

Staying on top of oil change intervals is also important to ensure that your engine runs with minimal energy losses, as is using the correct fuel and oils for your engine model. Software updates from the manufacturer may also be important for improving the performance and fuel efficiency of your truck.

While diesel fuel prices have been declining over the last several months, they still remain high. By using these eight rules of thumb you can control fuel consumption and optimize efficiency. | WA

Schedule a service appointment at one of Rush Truck Centers’ more than 140 locations to have their factory-trained, ASE-certified technicians make sure your vehicle is operating at peak fuel efficiency. Get in contact with their Rush Truck Centers Telematics Solutions team to learn more about their GeoTab® telematics solutions that are ideal for route optimization to save you time and reduce fuel consumption. To get started, visit www.rushtruckcenters.com.

1. As of November 20, 2023.
2. Based on diesel fuel prices as of November 20, 2023.