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First Diesel Truck? Here Are a Few Things To Know

A GMC 2500 HD Duramax 6.6 turbo diesel engine.

Congratulations, you’ve bought your first diesel truck! Now you can tow more, go farther between fill-ups and expect a longer lifespan for your vehicle.

Diesel engines aren’t just a gasoline engine alternative. Read on to see the other perks diesel engines bring to the tarmac.

Let’s Talk Torque

Diesel engines generate massive amounts of torque, the rotational force that the engine generates to turn the driveshaft, which then turns the wheels. Diesel engines not only generate more torque than gasoline engines but also do so at very low RPMs.

How Is That Different From Horsepower?GMC Sierra 2500 HD Diesel gauge cluster

Horsepower is usually measured as peak horsepower, and that peak comes after building up revs. Horsepower alone is not the right kind of power for moving, say, a four-horse trailer weighing 12,000 pounds from a standing start or a low speed. For that, you want torque.

Diesels produce more torque for a few reasons. First, they don’t use spark plugs. Instead, they heat the fuel to create combustion through much higher compression in the cylinders. A byproduct of this is more immediate power. Also, diesel fuel, unlike refined gasoline, has a higher energy density — more power in every drop. In addition, virtually all modern diesel engines are turbocharged. The result is pickup trucks that can tow up to 20,000 pounds, unlike their gasoline-powered siblings.

What Kind of Fuel Economy Should You Expect From Your First Diesel Truck?

As they say, your mileage may vary, but higher energy density means more motion from less fuel. Real-world numbers vary for different trucks, drivers and conditions. The U.S. Department of Energy reports that diesel engines get 30-35% better mileage than gasoline engines in the same vehicle. But diesel costs have risen (about 30-40 cents more per gallon) due to additional refinement to produce low-sulfur diesel fuels. The federal tax on diesel is also higher than the tax on gasoline.

What Is Diesel Exhaust Fluid?

Diesel Exhaust Fluid (DEF) is a mixture of urea and water that helps turn harmful emissions into nitrogen and water. It’s been required for all new diesel trucks sold in the USA since 2010. When the “DEF” dashboard light goes on, it means your DEF is running low. This will probably happen every 5,000 miles. Because this is a federally-mandated emission, you have a limited number of miles to resupply before the engine computer begins restricting speed.

Beyond that, maintaining your first diesel truck is pretty basic. In some ways, because of the lack of spark plugs, it’s simpler. Just be sure to follow your owners manual’s recommended maintenance schedule.

Check out all the diesel products available on NAPA Online, or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on your first diesel truck, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photos courtesy of Mike Hagerty.


Mike Hagerty View All

Mike Hagerty is an automotive journalist whose work has been featured on radio, TV, in print and online since 1997. He's the Publisher and Editor of, and contributes car reviews to the Los Altos Town Crier and Previous outlets have included KFBK and in Sacramento, California, the ABC television affiliates and Hearst-Argyle and Emmis radio stations in Phoenix, Arizona; AAA magazines for Arizona, Oklahoma, Northwest Ohio, South Dakota and the Mountain West and

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