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Diesel powers nearly every aspect of the supply chain at home and abroad. Of the 15 million registered commercial vehicles in the U.S., 76 percent run on diesel. With more torque and horsepower, higher towing capacities and longer lifespans, it’s no wonder so many businesses choose diesel. These engines are also besting their gas-fed counterparts in efficiency and fuel consumption, according to a 2024 highway driving test from Car and Driver. But the stats you love about your diesel will gradually decline without proper maintenance and considering other factors affecting performance. Learn how to use your newfound towing power responsibly. 

Diesel Maintenance Tips

Diesel engines may last up to a million miles or more, but their parts don’t. Many systems need significant rebuilds and repairs every 150,000 miles. The good news is that buying new diesel parts can help restore the truck to its original condition, increasing the resale value. Clogs, oxidation, leaks and mechanical wear and tear caused by poor lubrication prevent the engine from firing on all cylinders, literally and figuratively. 

The oil system lubricates moving parts while pressurizing the fuel to maximize power and efficiency. Diesel vehicles need oil changes every 5,000 miles, give or take 1,500 miles, depending on how much you tow. The air and fuel filters must be changed at most every 10,000 miles to prevent backstops and clogs.

If the oil pressure remains low after changing, replace the high-pressure pump to maintain fuel PSI levels. Dirty oil means another component is spreading debris and should be replaced. Low oil levels could signal a leak. 

Diesel engines use extreme heat and pressure to trigger combustion. The cooling system uses coolant to transfer heat to the radiator to prevent overheating. Heavy towing, high external temperatures and friction can overwhelm heat transfer components, causing cracks and leaks. The exhaust will emit blue smoke when coolant spills into the crankcase.

Check your fluid levels, including the oil, coolant and diesel exhaust fluid (DEF), before every trip to catch these early warning signs.

Towing (with Care)

Diesel engines were made to tow, but the extra weight inevitably reduces fuel efficiency and puts additional strain on various components. You can haul heavy loads without damaging the vehicle as long as you stay well within its weight limitations and increase the frequency of your maintenance routine, including more frequent oil, coolant and filter changes. Compare the vehicle’s gross weight, including the passengers, cargo and fluids, to the gross vehicle weight rating (GVWR) listed in the specifications and the weight of your trailer plus the fully loaded vehicle to the gross combined vehicle weight rating (GCWR). 

Uphill towing and long rides on hot days further strain the engine. If the weight is pushing the limit, make more trips when possible to err on the side of caution.

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Increasing Fuel Efficiency

Fuel efficiency varies depending on the weight and vehicle condition. If the MPG rating drops without towing, look to the oil or fuel system for a solution. You may have low fuel or oil pressure, which prevents the injectors from firing the fuel as a fine mist, making it harder to burn. This forces the engine to consume more fuel to generate the same amount of power as a well-maintained engine. 

Replace the fuel injection system pumps to maximize the amount of fuel the system can inject per rotation. High temperatures can also burn the cylinder nozzle heads, and excess debris can clog passageways, blocking the flow of pressurized fuel. 

Restoring the MPG rating can require trial and error. Move on to inspect the oil and coolant systems if efficiency remains low. 

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Emissions Reductions 

Diesel vehicles are subject to environmental regulations to limit the spread of carbon emissions and particulate matter, which causes climate change and is hazardous to human health. Most models have emissions reduction systems to offset the harmful effects of internal combustion. Failure to maintain these added components can lead to fines, compliance issues, internal damage and poor fuel efficiency. 

Engines that use selective catalytic reduction (SCR) need DEF to function. The fluid converts NOx into nitrogen and oxygen during combustion. Maintain DEF levels and inspect the exhaust for excess debris.

Exhaust gas recirculation (EGR) recycles part of the exhaust back through the engine instead of releasing it into the atmosphere. The EGR cooler lowers the temperature of the exhaust gas to prevent overheating. Inspect and replace the EGR cooler after 80,000 miles or less when towing heavy loads to prevent it from breaking down. 

Your Diesel To-Do List

Owning a diesel truck takes more responsibility than your average car or SUV. These engines use simple yet precise systems to generate the power you crave. Start every day by inspecting components and systems that determine performance, and monitor your real-time efficiency to see if the engine is working as well as it should. Taking the time to repair and maintain your investment will help it run like new for years to come.