4 Maintenance Tips to Improve Diesel Engine Efficiency

4 Maintenance Tips to Improve Diesel Engine Efficiency

When it comes to diesel engines, there’s one goal that all fleets have in common — improving engine efficiency. The more efficient a vehicle’s engine, the lower the operating and service costs, and the longer the service life.

With diesel fuel costs sky-high and the supply chain and new vehicle production issues of late, improving engine efficiency and extending service life is more important than ever. And the good news is, it’s not complicated to achieve.

Diesel Power

More than 15 million commercial vehicles are registered in the United States and 76% are powered by diesel engines. This percentage isn’t surprising, since diesel engines are known for their longevity, reliability, durability, and dramatically lower emissions. How low? It would take 60 new diesel trucks to generate the same emissions as a single diesel truck manufactured in 1988.

Keeping your fleet’s emissions low and your diesel engines reliable is as simple as following key maintenance tips to keep your engines in shape. Your engines will run smoother and more efficiently and your operations will benefit from:

  • Improved MPG
  • Lower maintenance costs
  • Decreased downtime
  • Strengthened vehicle resale value

1. Regular Cleaning

Since diesel vehicles tend to have a longer lifespan, navigate longer distances, and carry out more challenging tasks, contaminants such as dirt, dust, and grime can build up on the engine and significantly affect engine performance, efficiency, lifespan, and fuel efficiency. 

From the diesel injector to the filters, to the radiator, periodical cleaning with a specialized degreaser that’s formulated to dissolve gunk will keep the engine running efficiently and running longer.

2. Change the Oil

Oil is the lifeblood of an engine and the foundation of proper engine maintenance. Since diesel engines operate at higher temperatures, the chance of oil contamination is higher. To minimize premature failure, change the oil regularly.

Typical oil drain intervals are around 25,000 miles but vary depending on factors, including engine design, age, running conditions, driving patterns, and oil properties. Working with your engine manufacturer is key to setting the right oil drain intervals.

3. Check Coolant

Checking the coolant is crucial for efficient diesel engine operations. If a diesel engine is running on worn-out coolant you risk numerous engine problems and a productivity problem — being stranded on the side of the road.  

Since diesel engines are more demanding, they need cooling system maintenance more often than gasoline engines, typically every two years or 30,000 miles. But that said, inspect the coolant every six months to avoid engine issues. Look for these telltale signs that the coolant should be replaced:

  1. Empty or near-empty coolant reservoir
  2. Leaking water pump
  3. Cloudy or dirty radiator fluid
  4. Overheating engine 

4. Check Filters

Cleaning and changing the following diesel engine filters is critical to engine performance and efficiency.

Fuel Filters

Fuel filters ensure that the engine is supplied with clean fuel. When filters get heavily contaminated or clogged, they restrict or stop fuel flow, lowering engine performance or worse — preventing the engine from starting/running.

Fuel filter replacement times vary by operating conditions and engine age. A good rule of thumb is to replace the fuel filters of older engines every 10,000 to 15,000 miles and newer engines, every 15,000 to 20,000 miles — and replace all filters at the same time.

Oil Filters

Just as diesel engine oil requires changing, so do oil filters. Oil filters remove particles from the oil, which if not removed could cause engine damage and faster wear and tear. Ideally, change oil filters every oil drain interval.

Air Filters

Maintaining your diesel engine’s air filter improves fuel economy, lowers emissions, boosts acceleration, and prolongs engine life. Typically, the air filter should be replaced or thoroughly cleaned every 15,000 miles or every year, but that can vary depending on areas of operation and filter type. Signs that your filter needs replacing, include:

  • Lower MPG
  • Starting issues
  • Soot residue from the engine
  • Popping noises
  • Less horsepower
  • Excessive vibration
  • Black smoke coming from the exhaust

Diesel Particulate Filters (DPF)

Monitoring how your engine’s exhaust system is functioning is key to engine performance. A DPF filter is part of the exhaust system and traps particulate matter such as ash and soot. When the DPF filter becomes blocked or clogged, it can cause many problems, including:

  • Decreased engine performance
  • Poor fuel efficiency
  • Trouble starting
  • Presence of strange smells

If you notice any of these, replace or repair your DPF filter as soon as possible. A new DPF filter will help improve emissions, performance, and fuel efficiency.


The engine is the most important part of any vehicle. Proper maintenance is essential to ensuring it functions efficiently over a long period. The time and money invested in diesel engine maintenance are far less than the cost of serious engine problems. Keep your engine in shape, and you’ll help keep your bottom line in shape too.