5 Tips to Improve Semi-Truck Fuel Economy

The costs of driving include showers, dinners, truck maintenance and, of course, fuel.  Without diesel fuel, drivers wouldn’t get down the road. Semi-trucks have one to two fuel tanks that hold about 120 to 160 gallons each. If a truck has one tank on each side, it could hold up to 300 gallons of gas. 

Drivers need to have large amounts of fuel because the average miles per gallon (mpg) for semi-trucks is only 5.6 mpg. On a long route, fuel is consumed quickly. A semi-truck’s fuel efficiency can worsen when you include other factors, like inclement weather, steep roads and traffic jams.  

As diesel prices rise, you may be wondering how to get better fuel mileage in a semi-truck. Keep reading for tips to get more out of every fuel-up.

Diesel Prices On The Rise

Fuel is one of a trucking company’s biggest expenses. Up to 20% of operating costs for motor carriers are fuel expenses. 

The U.S. Energy Information Administration shares weekly updates on gasoline and diesel fuel costs. As of March 28, 2022, the average price of diesel in the U.S. is $5.185 per gallon. That price has increased by $2.02 since March 2021. 

Diesel costs vary by region. Prices per gallon remain higher on the East Coast, Rocky Mountains and the West Coast—particularly in California, where the price is $6.440 per gallon. Following typical trends, both regular gasoline and diesel cost less in the Midwest and Gulf Coast. In Missouri, diesel currently sits at $4.738 per gallon

Drivers could spend around $620 to $1,030 or more to fill up a tank. When you pay for diesel, your total cost is broken down to 53% for the crude oil, 16% for the refining processes, 17% for distribution and 14% for taxes. Crude oil prices have continued to increase since Russia invaded Ukraine on February 24, 2022, causing diesel prices to shift. 

Closeup of a semi-truck driver fueling up with diesel fuel. Closeup of hand on diesel pump.

Ways to Improve Gas Mileage on A Semi-Truck 

Ready to learn how to improve mpg? Better your semi-truck fuel mileage with these tips for reducing fuel consumption. 

1. Slow Down

Slowing down may be the last thing you want to do if you’re trying to make good time. Driving slower helps keep you safe and reduces the amount of fuel you use. The faster you go, the more fuel your truck consumes. 

Every 1 mph increase in speed translates to a decrease in fuel efficiency by 0.14 mpg. Over speeds of 50 mph, fuel efficiency quickly decreases. When drivers travel at speeds above 75 mph, they consume 27% more fuel than they do when driving at 65 mph. Every increase in speed takes more fuel. 

Let’s see how speed plays into a trip. For example, one driver travels 2,500 miles and gets 5.9 mpg at that time. If the driver increases speed by 10 mph, the driver will use an additional 132 gallons of fuel. At the current national price average ($5.185), that’s an extra $685 for diesel. Slowing down by 5 to 10 mph can save you money each trip. 

2. Use Cruise Control 

Cruise control is your fuel-saving friend. Aggressive acceleration and braking waste gas. Keeping your truck at a steady speed improves fuel efficiency. When you have the opportunity to use cruise control safely, it can save you up to 6% in fuel consumption over the course of your trip. 

3. Find the RPM “Sweet Spot”

RPM stands for “revolutions per minute,” and it measures engine speed. Semi-trucks use less fuel at lower engine speeds. If an engine has to work hard to maintain a speed, it will use more fuel. Slower speeds and lower revolutions per minute decrease overall fuel costs. 

Every truck has an optimal operating range. Engines are designed for high torque at low RPMs. When engines run at a lower RPM, they burn less fuel. What RPM is the most fuel-efficient? The answer depends on your truck model. The ideal range to run your engine is around 1250 to 1350 RPMs, not exceeding 1500 RPM.

4. Check Tire Pressure 

Could your tires help you cut down on fuel consumption? The National Highway Traffic Safety Administration (NHTSA) reports that properly inflated tires can save you $0.11 per gallon. Those underinflated tires do matter! A good rule to remember is that every decrease in tire pressure reduces fuel mileage by 0.3%. 

Standard tire pressure recommendations:

Type of Tire Tire Pressure (psi)
Steer Tires 110
Drive Tires 85 – 105 (95 average)
Trailer Tires 85 – 105 (95 average)

Keep the weather in mind as you travel. Temperature changes cause tire pressures to fluctuate. 

5. Reduce Idle Time

Drivers idle their trucks while waiting and resting. Most drivers wait for customers to load and unload inside their trucks. Many companies don’t allow drivers to wait inside their facilities. At night, drivers park, rest and sleep in their cabs. In these situations, idling is important for the driver—but it burns extra fuel. 

How much diesel does a truck burn idling? The U.S. Department of Energy found that idling a semi-truck wastes 0.8 gallons of fuel per hour. That doesn’t sound like much. But if a truck idles for 10 hours, it will use 8 gallons of gas, which would cost about $40. If a driver idled for 10 hours a day, idling would cost around $200 in fuel each week. 

On average, long-haul truck drivers idle for 1,800 hours annually. This idle time consumes about 1,500 gallons of diesel each year. Several states prohibit or limit idling for longer than 3 to 15 minutes. Some state idling laws include weather and traffic stipulations. 

You can reduce fuel costs by idling only when necessary and using alternatives, like auxiliary power units (APUs), automatic engine start/stop systems (AESS), or electrified parking spaces. APUs are common in most equipment today and included in all truck models that Prime Inc. offers. Some APUs run on diesel, while others run on batteries. 

As diesel prices fluctuate, use these tips to better your semi-truck fuel economy and stretch your hard-earned dollars. Slowing down, keeping speed consistent and reducing idle time help decrease fuel expenses and get you more miles out of every gallon. 

Are you ready to become a truck driver? Learn from the best at Prime Inc. We help you earn your CDL and start your over-the-road trucking career. 

Apply online today or contact our Recruiting Department at 866-290-1568 with questions about training, available jobs and life on the road.

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