2020 GMC Sierra 1500 Diesel MPG Test: As Good as Its Ratings?

2020 GMC Sierra 1500 Diesel  Side Profile Plus MPG Route

Cars.com illustration by Paul Dolan

By Aaron Bragman

During our first drive of the 2020 Chevrolet Silverado 1500 with the Duramax 3.0-liter diesel, our fuel economy results were astonishing after a 30-mile test loop being driven for maximum mileage: 38.1 mpg, according to the onboard computer. A slightly longer 70-mile drive with four people on board and elevation changes saw an average of 33.8 mpg, per the computer. Other journalists at the same event were showing 41-45-mpg returns, which beggars belief in a full-size half-ton pickup truck.

We needed to see what this engine could do in the real world on a much longer 200-mile fuel economy run under conditions we were familiar with, and on a route we had run dozens of times in other vehicles. Our chance came in a two-wheel-drive 2020 GMC Sierra 1500 SLT crew cab with the apparently magical turbocharged 3.0-liter "baby Duramax" diesel engine.

Related: 2020 GMC Sierra 1500 Duramax Diesel: Comparable to Ram 1500 EcoDiesel?

The engine itself is pretty special. It's an inline-six-cylinder turbo-diesel making 277 horsepower and 460 pounds-feet of torque mated to GM's 10-speed automatic transmission. We're told the official fuel economy ratings differ between the Chevrolet Silverado and GMC Sierra due to the significant aerodynamic differences between the two trucks and that the Silverado's wilder sheet metal is apparently more aerodynamic, whereas the Sierra's more traditional boxy shape is not. The Chevy is rated at 23/33/27 mpg city/highway/combined for the 2WD truck and 23/29/25 mpg for the four-wheel-drive model, but the GMC is a good bit less: 23/30/26 mpg for the 2WD, 22/26/24 mpg for the 4WD. That 3-mpg difference on the highway is telling for just how different the aerodynamics must be. Still, these combined ratings of 24-27 mpg are significantly different than the 38-45 mpg people were reporting at the launch drive of the Silverado. What's real here?

The Real-World Fuel Economy

Our test loop was a 200-mile jaunt of relatively flat southeast Michigan that included about one-third city driving under stop-and-go conditions and two-thirds 70-mph highway driving. Test conditions were ideal, with calm winds, blue skies and a temp at 64 degrees. Speeds were always kept to within 5 mph of the posted limit, tire pressures were set to the manufacturer's recommended values, climate control was always activated, windows were up, and I drove normally and calmly.

The results, while not as jaw-dropping as those seen on the launch drive, were still damned impressive. The 2020 GMC Sierra 1500 crew cab we tested consumed 6.4 gallons of diesel fuel over the course of 204.6 miles. That's good for an average combined fuel economy result of 32.0 mpg combined, or 6 mpg better than its official EPA combined rating and 2 mpg better than its highway rating alone. The truck's onboard computer was a bit more conservative, telling us that it was achieving 30.6 mpg combined over the test loop. Either way, that's a fantastic result, turning the Sierra into a viable commuter vehicle when its prodigious torque is not being used to tow a camper trailer or a boat.

When properly equipped, the Sierra 1500 with a 3.0-liter Duramax will drag up to 7,300 pounds in a 2WD crew cab with a long box and up to 9,100 pounds with a 4WD double cab. It does so effortlessly, as well. Smooth is the name of the game with the 3.0-liter Duramax; it's quiet, it's efficient, it provides plenty of usable around-town power, and it settles into a near-silent growl at highway speeds. Start to finish, GM has crafted a spectacular powertrain for its light-duty pickups, and the fact that it bests every other light-duty diesel on the market in terms of fuel economy (in Chevrolet trim but not GMC trim) isn't anything to sniff at, either. A 2020 Ram 1500 EcoDiesel 2WD is rated at 22/32/26 mpg, while a 2019 Ford F-150 Power Stroke is 22/30/25 mpg. It's a competitive set, but GM seems to be delivering more than it promises in terms of diesel fuel efficiency.

More From PickupTrucks.com:

PickupTrucks.com's Editorial department is your source for automotive news and reviews. In line with PickupTrucks.com's long-standing ethics policy, editors and reviewers don't accept gifts or free trips from automakers. The Editorial department is independent of PickupTrucks.com's advertising, sales and sponsored content departments.


The comments to this entry are closed.