A few simple things can wring more miles from a gallon of diesel
In mid-November, the average price of a gallon of diesel fuel was $3.734. That was up just a bit from the week before, but up $1.293 from 2020, according to the U.S. Energy Information Administration. As I have been driving my little big rig lately, I have regularly paid over $4 a gallon.
The American Transportation Research Institute reminds us that fuel represents nearly a quarter of a fleet’s total average marginal costs. So higher fuel prices have a significant impact on the fleet’s bottom line.
While there is not much fleets can do to control the price of fuel, there are some things they can do to use fuel more wisely.
The most obvious thing to do is slow down if possible. Driving at lower speeds reduces aerodynamic drag. A general rule of thumb is that for every mile per hour that is driven over 60 mph there is a fuel economy reduction of one-tenth of a mile per gallon. Look at your speeds and calculate what slowing down would do for your fuel expense. I know it is not always possible to slow down, but if you can it will be a big boost to your fuel efficiency.
Check inflation pressure on your tires. Underinflated tires are a big issue with a significant percentage of trucks running on underinflated tires. If a tire is underinflated by 10 PSI, fuel economy can take a 1% hit. Make sure drivers are checking inflation pressure on every tire during their pre- and post-trip inspections and make sure your technicians check tire pressure every time a truck is in the shop for service.
A well-maintained truck operates at an efficient level. Many fleets view maintenance as a cost center and may not see the link between a well-maintained truck and one that is fuel efficient. Fleets we spoke with for our Confidence Report on Preventive Maintenance—which we are in the process of updating—saw a 5% to 10% decrease on fuel consumption after implementing a rigorous preventive maintenance program.
The way you set engine parameters also can impact fuel economy. Our Confidence Report on Electronic Engine Parameters found that fuel economy improvements in the 5% to 8% range are possible for fleets when they optimize all parameters for fuel economy. Improvements of 3% to 5% above the defaults are possible for fleets that set the parameters of their new trucks in a few key areas such as vehicle speed and idle reduction.
Mechanical losses from pumping and friction consume approximately 16% of the total energy input of the vehicle. Lower viscosity oils—oils with less internal resistance to flow—will reduce these engine mechanical losses, thereby reducing fuel use. Fleets can expect to see a .5% to 1.5% increase in fuel economy when switching from a 15W-40 oil to a 5W/10W-30 and a .4% to .7% increase when switching to FA-4 oil from CJ-4/CK-4 5/10W-30 oils.
While fuel prices may be rising, there are some simple things fleets can do—many at no or little additional cost—to try to get as many miles per gallon out of that now expensive gallon of diesel.
Michael Roeth has worked in the commercial vehicle industry for nearly 30 years, most recently as executive director of the North American Council for Freight Efficiency. He currently serves on the second National Academy of Sciences Committee on Technologies and Approaches for Reducing the Fuel Consumption of Medium and Heavy-Duty Vehicles and has held various positions in engineering, quality, sales and plant management with Navistar and Behr/Cummins.
