Ways to Increase Diesel Fuel Mileage: Tips From The Industry

For trucking companies and fleets, diesel fuel is probably their biggest consumable expense, the biggest operating line item in their budget. It stands to reason that keeping a handle on fuel expenses is a high priority. No operation can completely control their fuel costs, but they all have some amount of control over it.

Certain rules are universal for virtually everyone in the industry when it comes to fuel consumption expenses. When you're trying to get the most out of your fuel budget, whatever you do is going to have to be worked in around these principles. You may already know some of these principles, but here are some ways to increase diesel fuel mileage:

Speed Matters

55 mph is the sweet spot for speed vs. fuel economy, or at least it is for cars. For most vehicles, including diesel fleets, fuel efficiency tends to peak at moderate speeds. According to studies and practical experience, the optimal speed for fuel efficiency is often found to be between 45 and 55 miles per hour (mph). Above this range, the fuel efficiency typically begins to decrease significantly. This is particularly true for large vehicles like trucks and buses that have larger frontal areas and, consequently, face more air resistance.

Tires Matter, As Well

The tires can have a dramatic impact on fuel use since they are the one part of the vehicle that makes contact with the road surface. The industry knows there are some tire rules they pay attention to:

• New tires can actually cut your fuel economy by up to 7% until they get broken in.
• Used lug tires can get up to 0.4 mpg better than new ones.
• You lose 1% fuel economy for every 10 psi that your tire pressure is underinflated
• The biggest fuel economy difference between old and new tires comes at speeds below 50 mph. As you go above 50 mph, aerodynamic influences become the biggest drag on fuel economy (see what we did there? Drag? Ha!)

There are other aspects and “hard rules” that could be commented on, but we want to save some more for later. The same engine manufacturers who point out these rules to us can also offer some helpful suggestions on things you can do to maximize your diesel fuel mileage.

Shifting Patterns Matter

Gear shifting patterns have a significant impact on fuel economy in large trucks, especially those equipped with manual transmissions. How and when the gears are changed influences better fuel economy by ensuring the engine operates within its most efficient rpm (revolutions per minute) range, often referred to as the "sweet spot." This is the engine's rpm range that provides the best balance between power and fuel efficiency. Operating outside of this range—either too low or too high rpm—can raise your fuel consumption.

Some shift patterns that can influence fuel mileage in a good way are Short Shifting and Progressive Shifting. Shifting gears at lower rpm (short shifting) can reduce fuel consumption by keeping the engine closer to its most efficient operating range. This short shifting practice avoids the engine operating at high rpm for prolonged periods, which consumes more fuel.

The sister concept, progressive shifting, involves using the gears progressively without skipping any gears (when conditions allow) and is designed to maintain the engine's optimal rpm range. You end up being more fuel efficient because you're ensuring that the engine works as efficiently as possible across different speeds.

Research and real-world trials have shown that optimizing shifting patterns can result in noticeable improvements in fuel economy. The specific fuel savings can vary depending on the vehicle, the driver, and the driving conditions, but studies have indicated that efficient shifting techniques can lead to fuel economy improvements of anywhere from 5% to 15%.

Idling Throws Money Away

In the course of operation, truckers have to idle at certain periods. You can’t just instruct someone never to do that. But if you can find shore power or truckstop electrification, that can help. Some analysts calculate that plugging in instead of idling can save more than $3,000 a year in fuel costs. That’s not pocket change, my friends.

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