How to Get Better Fuel Mileage in a Semi Truck

When looking at the operating budget of diesel fleets and trucking companies, the singular item that stands out in terms of being the biggest consumable expense would be diesel fuel. It is imperative to find as many ways as possible to lower the operating expenses for diesel fuel. Both truck manufacturers and diesel engine manufacturers agree that there are common rules to follow when trying to control fuel consumption costs. Specifically, we’ll try to address how to get better fuel mileage in a semi truck by applying some simple, yet powerful strategies.

One of the culprits that can cause inefficient diesel engine operation and a cut down on fuel economy would be any issues relating to fuel injectors. Most OEM diesel equipment manufacturers understand that today’s modern diesel fuels are causing increases in fuel injector issues. A typical injector problem from the past was deposits forming on the tips of injectors. Currently, these deposits are now being found internally. Whether the problems are external or internal on fuel injectors, both will lead to reduced fuel economy, a lack of engine performance, less power, and injector life being diminished.

How to Get Better Fuel Mileage in a Semi Truck

One simple strategy to implement is to choose a high-performance fuel injector fuel conditioner and cleaner. Looking for a diesel fuel additive that has a robust and heavy-duty additive package, along with a special lubricity agent, should help in cleaning up and removing harmful and fuel-robbing deposits by returning fuel injector tips to their original condition. The injector tips should now be able to create the proper atomized spray pattern.

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By treating your diesel fuel consistently with a high-performance diesel fuel conditioner and cleaner, you should notice an increase in fuel economy. Specifically, there are some niche specialized lubricant manufacturers that offer improved fuel economy up to 8% while utilizing their diesel fuel additive. For example, AMSOIL Diesel All-in-One Fuel Additive improves fuel economy up to 8%.

AMSOIL Diesel All-In-One.
AMSOIL Diesel All-In-One

The next recommended strategy that is quite easy to implement, yet can bring long-term benefits to your diesel engine, would be choosing the proper fuel mileage-improving motor oil. There are two choices when considering which type of motor oil to choose. Those two choices are conventional petroleum-based or synthetic. There are benefits to both if they are blended with high-quality base stocks and superior additive packages. It is possible for both types of motor oils to increase fuel economy. Still, for the sake of this blog post, we’re interested in maximizing fuel economy potential. With that in mind, the clear winner would be synthetic engine oils.

Benefits of Synthetic Engine Oil

The first reason is the difference in molecular structure between petroleum-based engine oils and synthetics. The molecular structure of petroleum base oils is irregular. In simple terms, the fluid flow of such oils is uneven and tends to create unnecessary fluid friction. Additionally, during cold starts and cold weather, these irregular-sized molecules can thicken and flow much slower and with more resistance, leading to wasteful burning of the fuel.

On the flip side, synthetic base oils are man-made and designed with molecules of all the same size. Synthetic base oils provide a fluid flow that is smooth, quick flowing, and reduces friction. During cold starts and cold weather, their molecules do not increase in size or thicken, but rather flow rapidly and do not waste unnecessary fuel.

AMSOIL Signature Series Max-Duty Synthetic Diesel Oil 5W-40.
AMSOIL Signature Series Max-Duty Synthetic Diesel Oil 5W-40

Now that synthetic engine oils are the choice for how to get better fuel mileage in a semi truck, let’s dig a little deeper into which specific synthetic motor oil can bring the greatest improvement in fuel economy. When a lubrication chemist is looking to formulate a fuel savings diesel motor oil, there are a few additives to consider. First would be the choice of a friction modifying additive.

As the name implies, its function is to reduce friction between two metals surfaces. By reducing friction, the engine is required to utilize less energy, which translates to having to burn less fuel. Depending on how far the chemist is willing to go when formulating an engine oil, he may add another additive to help in further decreasing fuel consumption.

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The next area to consider when choosing the best synthetic-based motor oil would be viscosity. Many off-highway and on-highway diesel engines are required to run in a vast range of temperatures and conditions. Conventional diesel engine wisdom sees most engine users typically running a 15W40 CK-4 engine oil. If your intention is to maximize your fuel economy, there is a better choice for a viscosity. By utilizing a 5W40 engine oil blended with 100% pure synthetic base stock oils, tests have shown an increase in fuel economy of 1% to 3% in comparison to a conventional petroleum 15W40 CK-4 engine oil. For all the reasons stated above, it is easy to see how this choice would lower fuel costs.

Extra Factors to Consider

Even though this blog post was specifically about how to get better fuel mileage in a semi truck, we’d like to add a few other fuel mileage-improving tips. In addition to utilizing a 100% synthetic engine oil, adding a 100% pure synthetic gear oil for both transmission and rear end will help reduce friction and contribute to your fuel improving goals. The speed that you drive definitely impacts fuel economy. 55 mph seems to be the optimum speed for maximizing fuel efficiency.

For example, AMSOIL conducted a test where a diesel truck was equipped with AMSOIL Synthetic Diesel Oil, Synthetic Transmission Fluid, and Synthetic Gear Oil and fuel mileage was improved by 6.54% in short to medium haul diesel applications.  During a second test, another diesel truck was equipped with  AMSOIL 100% Synthetic Diesel Oil, Synthetic Transmission Fluid, and Synthetic Gear Oil and fuel mileage was increased in stop and go city driving by 3.15%.

Next, tires can dramatically affect fuel consumption. A brand new tire can cut your fuel economy by as much as 7% until they’ve been properly broken in. For every 10 psi that your tire is under-inflated, you may lose up to 1% fuel efficiency.

Another area that can reduce fuel economy is revving your engine too much. It is best to shift to the next gear slower than normal. Unnecessary idling, though necessary for certain periods of time, can be costly. Whenever possible, use shore power, or truck-stop electrification, rather than idling. Statistics have shown that a diesel operator can save up to $3,000 a year in diesel fuel costs by plugging in rather than idling.

AMSOIL Diesel Injector Clean + Cetane Boost.
AMSOIL Diesel Injector Clean + Cetane Boost

Improve Fuel Economy & Restore Horsepower

When a fuel injector starts to have deposits form, these deposits can disrupt spray patterns, which can lead to poor fuel atomization, inefficient combustion, and too much smoke and emissions. More and more, diesel truck manufacturers are engineering high pressure common rail fuel systems so as to produce more power and still meet the tough government emission standards.

Injection pressures can reach 30,000 psi and higher in high pressure common rail systems. These high pressures help to atomize the fuel into a very fine mist for better combustion, increased power, improved fuel economy, and a reduction in emissions. To create and maintain these super high pressures, injector assemblies have been finely engineered and have very tight clearances as close as 1 to 3 microns in size. (In comparison, a human hair averages 70 to 100 microns thick.)

The smallest amount of internal diesel injector deposits that would accumulate on the injector pintel or other fuel injection components could cause sticking and even seizure, thus leading to a reduction in fuel economy, a decrease in power, and a loss in operability. Conventional additive chemistry is neither formulated for nor capable to handle and address these tough to remove deposits.

AMSOIL Diesel All-in-One was specifically engineered with a high performance chemistry that offers superior strength that helps to fight against internal diesel injector deposits and more common carbonaceous deposits. By addressing these problems, AMSOIL Diesel All-in-One Diesel Fuel Additive will restore horsepower and bring back your diesel engine’s like-new operability.

With consistent use of Diesel All-in-One, both acceleration and performance can be improved because this highly engineered diesel fuel additive helps to keep injectors clean from damaging deposits.

By improving fuel economy through the use of Diesel All-in-One, the semi truck owner/operator will benefit through the net savings on fuel, which can result in no additional cost of ownership.

Some of the other benefits beyond improving fuel economy through the use of AMSOIL Diesel All-in-One Fuel Additive is its ability to lubricate fuel pump components and injectors, which leads to a reduction in wear. Diesel All-in-One puts back the lubricity into the ultra low sulfur diesel fuels which are lacking in the necessary lubricating oils. By adding back lubricity, fuel pumps and injectors will last longer, perform better, and save on downtime and maintenance costs.

Increase Peak Performance By Improving Fuel Quality

AMSOIL Diesel All-in-One will improve the emission quality of diesel fuel by increasing cetane.  By increasing cetane, power is maximized and starting is improved. By improving fuel quality through the use of Diesel All-in-One, idle will be smoothed out and there will be a reduction in smoke and emissions.

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Helps Prevent Gelling

AMSOIL Diesel All-in-One will help to prevent wax settling during storage when temperatures start to drop. Also, during cold temperatures, Diesel All-in-One Fuel Additive helps to lower cold filter plugging point by up to 40 degrees F.

Save Money on Fuel and Motor Oil

When comparing conventional petroleum based oils vs. AMSOIL synthetic oils, the difference between the two lies at the molecular level. When refining crude oil to produce petroleum base oils, the refining process separates crude oil molecules by weight, thus leaving behind molecules of different sizes and shapes. Petroleum based oils have an inconsistent which requires much more power and energy to circulate the oil throughout your diesel engine. This extra consumption of power and fuel obviously leads to inferior fuel economy.

Additionally, conventional or petroleum based motor oils contain unstable molecules that are thermally unstable and tend to evaporate more easily when exposed to extreme heat. This volatility of conventional motor oils can cause your diesel oil to be consumed and the oil level to drop. If too much diesel motor oil is consumed, then if left unchecked, not enough oil is present to reach all the expensive and complex parts of your diesel engine. This could lead to possible catastrophic failure.

AMSOIL Signature Series Max-Duty Synthetic Diesel Oil 15W-40.
AMSOIL Signature Series Max-Duty Synthetic Diesel Oil 15W-40

On the flip side to this comparison of oils, AMSOIL synthetic lubricants utilize 100% pure base stock oils that are engineered and man-made. The manufacturing of synthetic base oils goes through a unique process that produces base oils that have a perfectly uniform molecular structure. AMSOIL synthetic lubricants contain pure and smooth molecules that slide easily and friction-free over one another. These synthetic base oils naturally offer superior lubricity when compared to conventional oils, thus reducing friction. This leads to superior and improved fuel economy.

Additionally, synthetic base stock oils are naturally more thermally stable when exposed to high temperatures, resulting in far less oil consumption.

Long Life Synthetic Gear Lube

AMSOIL 80W-140 Long Life Synthetic Gear Lube.
AMSOIL 80W-140 Long Life Synthetic Gear Lube

As we’ve already discussed in that synthetic motor oils offer a fuel economy improvement vs. petroleum based diesel oils, the same fuel economy benefits can also be realized when switching from conventional gear oils to synthetic gear lubes. AMSOIL offers various synthetic gear lubes that can greatly enhance the performance of any semi truck. Not only can fuel economy be improved, but also there can be benefits realized such as superior cold weather shifting, protecting gears from rust and corrosion, superior bearing and gear protection from extreme pressure and high loads, improved efficiency, and longer seal life.

When both synthetic motor oil and synthetic gear oils are utilized, together they create a synergistic performance that will help to improve overall fuel economy for the semi truck owner/operator.

Long Life Synthetic Transmission Oil

AMSOIL SAE 50 Long-Life Synthetic Transmission Oil.
AMSOIL SAE 50 Long-Life Synthetic Transmission Oil

Beyond diesel motor oil and gear oil, even more fuel economy improvements can be gained through the use of an SAE 50 long life synthetic transmission oil. AMSOIL has custom formulated such an oil to meet the stringent requirements of manual transmissions found in high torque heavy duty line haul trucks and other applications. AMSOIL chemists have chosen only the finest base stocks and the absolute top of the line premium additives in this superior transmission fluid. Its unique chemistry can deliver performance for 500,000 miles of service in over the road trucks.

Not only does it offer long life, but this unique synthetic transmission oil will help to reduce bearing and gear wear, deliver smoother shifting, and extend the service life off the transmission, all the while still providing safe drain intervals of up to 500,000 miles or 5 years. Remember, because it utilizes the finest friction reducing synthetic base stock oils, there can be additional fuel mileage gains through the use of this unique AMSOIL lubricant.

Hopefully, we’ve provided some food for thought on how to get better fuel mileage in a semi truck.