Gasoline versus diesel. It’s an age-old engine debate — and one that keeps popping up as technology and fleet needs continually evolve. Where does it stand for today’s light- and medium-duty trucking fleets? OEM experts weigh in.

Acquisition and Fuel Costs

Let’s start at the beginning: up-front costs.

Nathan Oscarson, brand manager for Ford commercial trucks, said diesel trucks cost around $10,000 more up front than similarly spec’ed gasoline trucks. But, there is a reason.

“Diesel engines, such as our third-generation 6.7L Power Stroke, are built for the worst-case scenario. This engineering and testing, along with the cost and maintenance of emissions equipment, can increase the initial investment and long-term maintenance costs of a diesel engine,” he said. “Ford gasoline trucks have become very popular with fleet managers because they are significantly more affordable and require less maintenance.”

If you’re looking at up-front costs alone, gasoline gets the advantage. Gasoline-powered trucks also win on the cost per gallon of fuel. But again, there’s a caveat.

“Diesel is generally more expensive,” said Dave Sowers, head of Ram Commercial Marketing. “At the same time, diesel fuel has a higher density than gasoline, meaning it needs less fuel to generate the same power as a gasoline-powered engine. So, diesel engines can provide superior fuel economy to gasoline engines.”

For instance, Sowers explained that the 2020 Ram 1500 EcoDiesel features a highway rating of 29 mpg for 4×4 models, compared to a 21 mpg for a typical gasoline engine truck. So, while the cost of diesel averages $0.50 more per gallon, the vehicle has improved fuel economy.

Greg Baker, product director for Mitsubishi Fuso Truck of America, said this improved fuel economy could make up for the higher sticker price, especially for high-mileage fleets.

“If the customer has high mileage, a diesel truck may make more sense because of the improved fuel economy. The improved fuel economy may help offset the higher initial investment cost of the diesel truck,” he said. “However, most light- and medium-duty truck applications are not high-mileage-type vehicles, which can make gasoline trucks more economical.”

Maintenance Differences

When it comes to maintenance, each engine type has its unique demands — and those can make a meaningful difference.

For instance, diesel engine components require service for fuel filters and diesel exhaust fluid (DEF). Gasoline engines, on the other hand, have shorter oil change intervals and require periodic maintenance on spark plugs that don’t exist on diesel engines.

“While maintenance of a diesel engine costs more per occurrence, intervals can be extended compared to a gasoline engine,” said Sowers of Ram Commercial. “For example, Ram Heavy Duty pickups equipped with a Cummins Diesel engine can extend oil change intervals to 15,000 miles.”

Although both engine types have unique requirements, Oscarson of Ford said maintenance for diesel-powered engines tends to be more costly and difficult.

“A fleet manager must have a plan in place for diesel maintenance, as it is more complex and specialized then gasoline engine maintenance and repair,” he explained. “Maintenance for diesel trucks can be more expensive because it requires specialized training. And, there are not as many diesel service facilities as gasoline engine repair facilities.”

Then there’s the DEF factor, which doesn’t pertain to gasoline-powered engines.

“More maintenance is required on a diesel with the DEF fluid that needs to be added to the truck about every 2,000 to 3,000 miles,” said Brian Tabel, executive director of marketing for Isuzu Commercial Truck of America. “The diesel particulate filter (DPF) also needs to be serviced and cleaned at every 100,000 miles, which is an additional maintenance cost.”

Putting it all together, Baker of Mitsubishi Fuso said gasoline gets the advantage when it comes to maintenance.

“Diesel trucks have significantly greater overall maintenance costs even with the longer intervals between service dates,” he said. “The reason for this is that gasoline engines have a more simplistic emissions system compared to the more complex diesel emissions system. The diesel truck also requires additional consumables such as DEF fluid.”

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