Posted on

How to Make a Diesel Engine More Fuel Efficient

Featured image for "How to Make a Diesel Engine More Fuel Efficient" blog post. Blue semi truck.

If there was a way to learn how to make a diesel engine more fuel efficient, the majority of diesel fleet owners would jump at the chance. This blog post will propose two very simple strategies that could increase fuel economy by as much as 9.5%. That may seem like a fairy tale, but there are diesel operators that have followed these two approaches to gain this type of improvement.

What Causes a Diesel Engine to Lose Its Fuel Efficiency?

Once of the main issues causing diesel engines to run inefficiently and deliver poor fuel efficiency would be deposits forming on fuel injectors. Diesel fuel is forever changing in quality and this causes injector problems. In the past, deposits tended to form on the tips of injectors. Now, these same deposits are starting to form internally. Today, there are low sulfur, ultra low sulfur, and bio-based diesel fuels.

To refine these low sulfur diesel fuels, much of their natural lubricity has been taken out. The refining process to create such diesel fuels has resulted in fuels that are weaker in a few areas. They are weaker in thermal stability, and they are weaker in the level of antioxidants. Coupled together with weaker fuels and combining that with the highly engineered injection systems, these fuels are forced to operate at much higher temperatures.

What is causing the problems is not the injection systems, but the varying degrees of quality of diesel fuels available to diesel operators. Because these fuels are susceptible to being thermally unstable and prone to oxidation, both these problems leads to deposits forming within the injectors. When this happens, the precise spray patterns that are required for maximum engine efficiency and fuel economy become compromised.

Instead of a perfectly even spray pattern, the deposits start to cause uneven spraying. Over time, if left unchecked, engines lose power, efficiency, and waste precious costly fuel.

Silver semi truck on the road.
Deposits inside injectors are caused by the varying and lower sulfur diesel fuels. The result, unfortunately, is poor fuel efficiency and reduced engine power because of injector spray patterns being adversely affected.









How to Make a Diesel Engine More Fuel Efficient

Use a High Performance Fuel Treatment

A simple yet effective strategy would be to use a high-performance diesel fuel treatment. There are some experienced and clever lubricant manufacturers that are designing diesel fuel additives that actually deliver on the benefits they claim to provide. Look for a diesel fuel treatment that utilizes a heavy oil base rather than an alcohol-based formulation. Such a product will provide critically needed lubrication to the upper cylinder and ring area of an engine and also protect critical components of the fuel pump and injectors.

Conduct your own research to be sure that the specialized diesel fuel treatment provides superior fuel injector cleaning. The goal is for the fuel conditioner to safely soften and dissolve accumulated deposits found either on the tips of the injector or internally. This is accomplished through advanced chemistry that effectively should clean up a dirty fuel system.

The goal is to get the injectors as clean as they were when new. A quality fuel additive should be able to accomplish this over time. Once this is reached, then the diesel engine should be able to reach maximum combustion efficiency. In-the-field testing usage of such a diesel fuel additive has delivered diesel operators fuel economy improvements as high as 6.5% after cleaning the injectors with such a diesel fuel treatment.

This is one simple solution in how to make a diesel engine more fuel efficient. Of course, beyond fuel economy, any lost engine power will be returned along with increases in power. Also, another added benefit to these specialized diesel fuel additives would be reduced exhaust emissions, which is an important benefit due to stricter government environmental regulations imposed on diesel operators.

Fuel truck on the road.
If fuel economy robbing deposits can be removed from the injectors, then there is the potential of 6.5% better fuel efficiency.








Digging a little deeper into the benefits in using a custom blended diesel fuel treatment that improves diesel fuel economy would be how it deals with maintaining fuel stability and providing corrosion protection. A well engineered diesel fuel conditioner should provide and maintain diesel fuel stability and protection against fuel oxidation. Solving these two issues will prevent sludge and filter plugging, as well as prevent deposits.

Corrosion is always a potential issue for diesel fuel system components. If critical parts start to corrode, the life of the engine is reduced, maintenance costs rise, and engine performance starts to diminish. It is important to be sure that the diesel fuel treatment chemistry contains robust volumes of corrosion inhibitors. These corrosion inhibiting agents will protect fuel systems from rust and corrosion.

Utilizing a Synthetic-Based Engine Oil

The second strategy we propose in how to make a diesel engine more fuel efficient would be determining whether moving to a synthetic-based motor oil could bring fuel economy improvements. There are major differences between conventional diesel motor oils and synthetic-based diesel engine oils. Structurally, conventional motor oils utilize base stocks whose molecular structure is uneven and of different sizes. What this means is that the motor oil does not flow easy. This translates to excessive fluid friction.

These unevenly sized molecules require the engine to expend more energy because of the fluid friction it is causing. Beyond the basic molecular structure of conventional diesel oils is the fact that they have unwanted byproducts that over time leave damaging deposits. The buildup of deposits such as gum, varnish, and sludge can cause an engine’s performance and efficiency to drop. All this contributes not only to inferior fuel efficiency, but a lack of power and a reduction in engine life.

Semi truck on the road near a farm.
Can changing to a synthetic based motor oil improve fuel efficiency? Experience has shown that this is definitely possible.








Diesel engine oils that are based on synthetics utilize oils that are essentially made in a laboratory. Their molecular structure is even and of the same size. This is significant when the goal is to improve fuel efficiency. When the molecular structure is even, the oil flows evenly and with far less fluid friction. By utilizing an engine oil that flows easy, this means the engine will expend far less energy. When an engine uses less power, this translates into a savings in fuel because less of it is burned.

Additionally, the base oils used, along with the synthetics, are highly defined. They are put through three separate and rigorous blending processes to extract and eliminate all unwanted byproducts. The end result are superior base oils that protect the engine far better and with minimal, if any, deposits. Also, they withstand much higher temperatures because of their superior thermal stability and resistance to oxidation. Remember, if an oil can withstand excessive heat and is resistant to oxidation, your diesel engine will stay clean and protected.

At this point, we can see that some of the added benefits offered by a synthetically blended diesel engine oil  are that your engine works easier, more efficiently, and burns less fuel. Next, it is important to look at the additive chemistry that is blended into these specialized base oils. With the same goal of improving fuel economy, it is critical that the engine oil incorporate friction modifying additives and any specialized additives, such as moly, that are proven to further reduce friction.

Moly has a long history in the lubricant industry. It is an interesting product that withstands high temperature, extreme pressure, and when used to protect metal, will radically reduce any frictional action. When an oil is formulated with friction reducing base oils and friction reducing additives, then the chances of getting better fuel economy have been greatly enhanced with this combination.

Yellow dump truck.
Not only can a synthetically blended motor oil increase fuel economy, but if it also utilizes friction reducing moly, then improvements in fuel efficiency can be even greater.








There’s one other benefit that needs to be mentioned in regards to using a synthetic based engine oil that includes friction-reducing additives such as moly. More than 80% of engine wear occurs at initial startup. Since synthetic base oils flow easier than conventional oils, then during startup, an engine will turn over easier and experience less wear with synthetics. Utilizing an oil that has moly further helps cold weather start ups due to its ability to prevent dry starts and its ability to reduce friction.

The last factor to consider in how to make a diesel engine more fuel efficient would be choosing its viscosity. To get maximum fuel efficiency, choose a 5W40 high-performance diesel oil over a 15W40. By going down to a 5W40, cold weather performance is vastly improved. The oil throughout all temperatures will flow with less friction, but still give maximum protection during extreme temperatures and engine loads. This moly synthetic-based motor oil, with a viscosity of 5W40, has delivered as much as 3% better fuel efficiency. Adding the diesel fuel additive treatment benefits of 6.5% better fuel economy together with the 5W40 synthetic blend motor oil, a 9.5% total fuel efficiency improvement is doable.

Logging truck on the road in winter.
Choosing the most fuel efficient engine oil viscosity is another factor in helping reach fuel improvements. A viscosity of 5W40 is an example of a fuel economy enhancer.