The 2020 GMC Sierra 1500 Duramax diesel pickup is a V-8 alternative

August 28, 2019

Truck buyers in the U.S. have drastically transformed in the past several years. Between more available mid-sized trucks and full-size overhauls that have challenged traditions, buying a truck is harder now than it ever has been.

GMC makes buying a truck even more complicated for 2020 with the (belated) introduction of a 3.0-liter turbodiesel inline-6 for its Sierra 1500 lineup. GM originally planned to introduce the engine with the rest of its Chevrolet Silverado and GM Sierra lineup in 2019, but delays in the EPA certification pushed that back.

Not long ago, diesel engines were strictly the domain of heavy-duty pickups. Now, Ram's light-duty diesel has returned for a second generation and Ford offers an F-150 diesel model. With Chevrolet checking in and GMC now finally throwing its hat in the ring, suddenly, the diesel-truck segment seems awkwardly busy. The times, they are a-changing.

Where these new diesel pickups fall into the overall pickup truck hierarchy is still open to debate, so we accepted GMC's invitation to drive the new Sierra 1500 Denali Duramax diesel in Jackson, Wyoming, to see for ourselves what the new engine does for GM's premium workhorse. 

We first drove the 2019 GMC Sierra 1500 a year ago. Conveniently, the truck remains essentially unchanged for 2020 outside of a few new options (of which the 3.0-liter Duramax is the most notable), which allowed us to focus on the new engine offering in our limited time with the 2020 model. 

The only vehicle offered with the new turbodiesel for on-road testing was a Denali, which is the range-topping model in the Sierra 1500 lineup. The downside to GMC's decision to not make any other changes to the 2020 lineup is the fact that the Denali's interior remains decidedly unimpressive, especially when compared to the Ram 1500's. This is especially egregious when you consider that Ram is not explicitly playing to a premium niche the way GMC is.

Fortunately, the diesel itself is not a particularly expensive option. At the time of publication, GMC had not yet provided us with a pricing structure for the 2020 Sierra 1500 Denali, but information leaked for the 2019 model year listed the diesel at $2,495. This is the same price premium as the 6.2-liter gasoline V-8. 

2020 GMC Sierra 1500 Duramax

2020 GMC Sierra 1500 Duramax

On paper, these are two very different engines. The 3.0L inline-6 turbodiesel makes 277 horsepower and 460 pound-feet of torque. The 6.2-liter V-8 makes 420 hp and 460 lb-ft of torque, making it the undeniable king of the light-duty performance hill. In its most efficient configuration the 3.0-liter diesel is rated at 23 mpg city, 30 highway, 26 combined. On the other hand, the 6.2-liter V-8 tops out at just 15/20/17 mpg, according to the EPA.

Despite the identical torque figures, the gas V-8 has the better towing capacity, and it it isn't even close. In optimal configuration, you can put 12,100 pounds behind the 6.2-liter. The diesel? Just 9,800 pounds.

We were curious to see just how the diesel acquitted itself with a load hitched up. On our first day in Jackson, we snagged the keys to a Denali with an 8,000-pound trailer hitched to it and set off on the GMC-prescribed, 15.6-mile loop. The route followed the same roads out and back, and included speed limits varying from 35 to 65 mph and a half-mile, 6-percent grade to test the diesel's grunt going uphill and its braking headed back down. 

While the little diesel had adequate power for the job, it was not exactly eager to get up and go with such a heavy trailer. The tachometer read nearly 3,000 rpm as we climbed the steepest grade. That's screaming for a diesel, but to its credit, it did manage to maintain the 55 mph speed limit despite the load. That's no small feat. At the end of the loop, we'd averaged 12.6 mpg. 

After returning the trailer, we managed to sneak off with an unladen Denali (configured the same way, conveniently) for comparison. Less the trailer, we found the 1500 Duramax was quiet and composed, with very little in the way of intrusive engine noise. This is particularly noteworthy for a diesel-powered truck, as oil-burners tend to be louder than their gasoline counterparts. More impressive, however, was the diesel's fuel economy performance. Unencumbered, it managed 27.2 mpg.

We spoke to GMC's spokespeople, who told us the Duramax models are intended to slot between the 355-horsepower, 5.3-liter V-8 and the 6.2-liter engine we mentioned above. Considering that both the diesel and 6.2-liter cost the same, we think it's a bit more nuanced than that. The 6.2-liter offers performance and maximum capability at the expense of fuel economy. The diesel, for the same price, flips that script.

In fact, the diesel is far and away the most efficient engine offered in any GMC Sierra pickup. Even the available 2.7-liter turbocharged inline-4 does no better than 23 mpg on the highway. For those who drive long distances on a regular basis and need some towing capability, the diesel makes sense. 

GMC provided travel and lodging to Internet Brands Automotive to bring you this firsthand report.

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