Tips for Better Semi Truck Fuel Efficiency
July 13, 2021
Have you seen your fuel costs climbing? As global shipping reaches new heights while diesel stockpiles run low, diesel prices are booming. Diesel hit $3.30 per gallon in the final week of June, the ninth consecutive week of increases, according to the Energy Information Administration. With diesel now 87 cents more than it was a year ago, fuel economy is becoming more of a priority than ever. Average fuel economy for Class 8 trucks still hovering around 5.97 miles per gallon. The North American Council for Freight Efficiency (NACFE) Annual Fleet Fuel Study found a fleetwide average of 7.27 miles per gallon among participants in 2018. And during the Run on Less 2017 test period, fleet performance averaged 8.5 to 11.5 miles per gallon. To say there’s room to improve is a massive understatement.
Read the full Run on Less 2017 Report
Summary: Run on Less is a cross-country roadshow organized by NACFE intended to showcase current efficiency technology. The 2017 run featured seven fleets running currently available technology and represented large, medium and small fleets and one owner-operator running routes representative of the majority of truck traffic. In total, these seven trucks averaged 10.1 mpg over the 17 days of the trial, compared with a national average of 6.4 mpg. Overall, this roadshow demonstrated that 10 mpg can and does happen in the real world, but it takes work.
Average Semi Truck Miles Per Gallon Through the Years
Over the last 70 years, semi truck gas mileage has improved by leaps and bounds, jumping from 4 to 5 mpg despite adding 20 feet in length to trailers and increasing gross weights by nearly 7,000 pounds. Today, as the average semi truck miles per gallon for newer vehicles hovers in the 7 to 8 mpg range, 10 mpg can seem far away. While that leap will require an over 50% improvement in fuel efficiency, it’s not as far off as it may seem. Some fleets with highly efficient trucks and drivers are already seeing average miles per gallon over 10. Super trucks are even seeing as high as 12. Getting your fleet closer to that 10 mpg barrier will take a combination of smart truck purchases, smart fleet managers and smart drivers.
New Technologies Paving the Way for Improved Miles per Gallon
If your aim is to get your fleet’s average miles per gallon up, purchasing a new truck with the most advanced fuel-saving technology will go a long way. But with semi truck inventory so hard to find (find out more about what’s happening with inventory), there are still plenty of retrofitting options that improve your existing truck’s average miles per gallon. Each type has its own considerations and costs. We’ll cover a few to take into consideration and whether they’re worth it to retrofit or wait to buy new.
Electronically controlled transmissions: Over the last decade, the adoption of electronically controlled transmissions has jumped dramatically, and with good reason. Testing shows that fleets with automated manual transmissions (AMT) can expect to see a 1-3% improvement in fuel efficiency. Per truck, that adds up to around $2,500 saved annually. And fuel economy isn’t the only benefit. Upgrading to an AMT makes driving easier and more comfortable, improving driver retention because driving is less tiring, which leads to better driver safety and performance. AMTs do have their downsides, namely a higher upfront cost and higher maintenance costs.
Interested in learning more about AMTs? Read our blog on the Volvo I-Shift transmission.
Low Rolling Resistance Tires: Low rolling resistance (LRR) tires have been calculated to save a significant amount of fuel. Rolling resistance accounts for 30-33% of the total fuel cost of a modern, aerodynamic Class 8 truck. The EPA SmartWay list now contains over 300 tire brands with verified LRR tires. LRR tires do cost slightly more than traditional tires, and can wear out slightly faster as well. Still, the fuel savings can’t be beat. One issue to keep in mind though, most manufacturers don’t publish their rolling resistance coefficients, so there can be big differences between SmartWay verified tires. If you’re not using LRR tires, the choice is simple; make the switch! If you are, a trustworthy tire rep and consistent testing will get you the difference you’re looking for.
Trailer Aerodynamics: A more aerodynamic vehicle requires less fuel to move it; that’s a pretty basic idea. But the difference trailer aerodynamics can make on fuel consumption can be significant, sometimes up to a 10% improvement. Much of the industry research into trailer aerodynamics has focused on basic vans, with improvement devices used in three different areas: the gap, the underbody and the rear. Trailer skirts are one popular option you’re probably familiar with. They’re relatively inexpensive, widely tested and offer up to a 5% improvement in fuel economy. Trailer rear devices are less popular and have seen less testing, but newer generation devices are definitely showing their worth. If you already have trailer skirts and are looking for the next step, a rear device is it. Finally, aerodynamic gap devices aim to seal the gap between truck and trailer while at highway speeds. These devices can be more expensive, but as they increase in popularity, you can expect the price to drop.
There are tons of other devices and additions that can reduce your fuel costs. The right engine for your routes can make a huge difference. Check out our blogs on choosing the right Mack engine or Volvo engine for your truck. Also be sure to check out the North American Council for Freight Efficiency’s Confidence Reports to learn more about their fuel efficiency studies.
Driving Strategies and Practices
All the upgrades and new technology in the world won’t save you fuel if your drivers aren’t working with fuel economy in mind. Here are a few of our tips to use when driving to make the most of your fuel-saving technology.
- Slow down! Above 55 mph, each 1 mph increase reduces fuel efficiency by .1 mpg.
- Coast when possible. Using the truck’s own momentum can save fuel.
- Try to stay in top gear at least 85% of the time of the distance in a normal highway application. Let the engine lug down when slowing.
- Make as few shifts as possible, shifting between 1150 and 1500 rpm.
- Keep a close eye on tire inflation. If you want to learn more about tire inflation, check out our guide on tire inflation.
What not to do
- Avoid major speed changes. Each 0 to 65 mph acceleration uses up to half a gallon of fuel.
- Avoid idling whenever possible. Each hour of idle time can decrease fuel efficiency by 1%.
Other factors that affect fuel efficiency
- The driver is the biggest contributor to miles per gallon at any speed. After that, tires are the most important factor below 55 mph, while above 55mph it’s aerodynamics.
- Each 2% reduction in drag results in 1% improvement in fuel efficiency when driving above 55 mph.
- Fuel efficiency can increase up to 7% after tires are broken in (which occurs at 35,000-50,000 miles).
At the end of the day, the driver is the key to vehicle performance. That’s why effective driver training can pay off almost immediately. Tests show drivers who adopt more fuel-efficient driving techniques can reduce fuel cost by 5% or greater. Combine a smart, well-trained driver with a fuel efficient drivetrain and plenty of fuel efficient devices on the tractor and trailer, and you have a recipe for savings.
Interested in making fuel efficient upgrades to your semi truck or trailer? Our parts teams are stocked up and ready to help you find the fuel efficient parts that will save you money.