GMC Sierra 1500 AT4 Diesel
2020 GMC Sierra 1500 AT4 Crew Cab in Satin Steel Metallic (a $495 option)

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2020 GMC Sierra 1500 AT4 Crew Cab

Class: Large Pickup Truck

Miles driven: 214

Fuel used: 7.8 gallons

CG Report Card
Room and ComfortA
Power and PerformanceA-
Fit and FinishB-
Fuel EconomyA
Report-card grades are derived from a consensus of test-driver evaluations. All grades are versus other vehicles in the same class. Value grade is for specific trim level evaluated, and may not reflect Consumer Guide's impressions of the entire model lineup.
Big & Tall Comfort
Big GuyA
Tall GuyA
Big & Tall comfort ratings are for front seats only. "Big" rating based on male tester weighing approximately 350 pounds, "Tall" rating based on 6'6"-tall male tester.
Engine Specs277-hp 3.0-liter
Engine TypeTurbodiesel 6-cyl
Transmission 10-speed automatic
Drive Wheels4WD

Real-world fuel economy: 27.3 mpg

Driving mix: 25% city, 75% highway

EPA-estimated fuel economy: 22/26/24 ( mpg city, highway, combined)

Fuel type: Diesel

Base price: $53,700 (not including $1595 destination charge)

Options on test vehicle: AT4 CarbonPro Edition Package ($4415; includes AT4 Premium Package, AT4 Preferred Package, and Driver Alert Package 1), 3.0-liter Duramax turbodiesel inline-six engine ($2495), Satin Steel Metallic paint ($495), rear under-seat storage ($265)

Price as tested: $62,965


Quick Hits

The great: Excellent fuel economy for a full-size pickup; spacious interior

The good: Cabin-storage space; functionality of MultiPro tailgate

The not so good: Interior ambiance isn’t quite up to the standards of comparable class rivals; road roar from all-terrain tires

More Sierra price and availability information


CG Says:

OK, it was a little late, but GMC ultimately kept its promise. When a redesigned full-size Sierra 1500 pickup was launched for 2019, there was a pledge to add a turbodiesel engine option at some point during the model year. Well, maybe an old friend came in from out of town. Maybe there was an earthquake! A terrible flood! Locusts! Bottom line, no oil-burner.

GMC Sierra 1500 AT4 Diesel
The 6-inch black rectangular bodyside assist steps come with the AT4 Premium Package, which is automatically included in the AT4 CarbonPro Edition Package. Built-in rear bumper steps are handy as well.

Until now. GMC (with corporate cousin Chevrolet) makes the 3.0-liter inline 6-cylinder powerplant a new talking point for the 2020 model year. It’s the first diesel available for General Motors’s half-ton trucks, and it catches them up to Ram and Ford, both of which have 3.0-liter turbodiesel V6 options for their lightest big pickups. GMC makes it available in Sierra SLE, Elevation, SLT, AT4, and Denali models, and Consumer Guide got to try it out in an off-road-oriented AT4 crew cab.

First Look: 2019 GMC Sierra 1500 CarbonPro Edition

2020 Sierra Diesel
Though it doesn’t present as well as similarly priced Ram 1500 models, the Sierra AT4’s interior  is nicely finished. A wireless charging pad (located at the front of the center console) is included in the AT4 Premium Package.

We won’t dwell much here on the driving character and environment of the AT4, considering that we reported on the 2019 job in First Spin and Test Drive posts. As a quick reminder, it’s the 4-wheel-drive Sierra with a 2-inch suspension lift, skid plates to protect the underbellies of important mechanical systems—like the two-speed transfer case—off-road-tuned shock absorbers, specific exterior trim, and a distinct Jet Black/Kalahari interior with perforated-leather front seats.

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2020 Sierra Diesel
AT4s wear unique “Kalahari” caramel-colored accents within their Jet Black upholstery. As expected, occupant space is generous in both the front and rear seats.

The new Duramax turbodiesel six produces 277 horsepower which is more than the competing Ram or Ford diesels make. However, the Duramax’s torque rating of 460 lb-ft is second, trailing the Ram mill by 20 lb-ft. At least the GMC engine finds its torque peak in a hurry, attaining full strength as soon as 1500 rpm. It starts and idles relatively quietly; you have to prod it to produce a degree of traditional diesel clatter. It’s not a sprinter off the line, not like the 6.2-liter gas-V8 AT4 that CG previously tested, but the 10-speed automatic transmission helps an unladen diesel AT4 smoothly work its way up to easily maintained highway speeds, and it kicks down quickly to assist merging and passing power. As for pulling power, though, the “Jimmy” is well off the pace. The best it will do with a diesel is 9100 pounds as a 4×4 with the shorter Double Cab. That’s more than 200 to 300 pounds less than the towing limits of Ford and Ram diesels.

EPA estimates for 4-wheel-drive diesel Sierra 1500s are 22 mpg in the city and 26 mpg on the highway. In a somewhat short test span, our editors managed to top 27 mpg with a majority of free-rolling expressway driving.

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2020 Sierra Diesel
The Duramax turbodiesel 6-cylinder engine adds a significant $2495 to the bottom line, but it delivers outstanding fuel economy and decent power. AT4s come standard with 18-inch machined aluminum wheels with Dark Grey accents.

The Duramax option is a $2495 upcharge (the same cost as the 6.2-liter V8). It brought the starting price, with delivery, of the test truck to $57,790.

CG’s tester came with the “short” 5.8-foot cargo bed, but it was a well-equipped bed. That’s because the truck was outfitted with the CarbonPro Package that features an innovative carbon-fiber composite pickup bed with the MultiPro tailgate that can fold out to create access steps. The package fits a Kicker audio system into the MultiPro assembly, which should make a great accompaniment to, uh, tailgating. Other package features are a black-chrome grille surround, black dual exhaust tips, 18-inch mud-terrain tires (though 20-inch all-terrain rubber is available), and running boards.

GMC Sierra 1500 AT4
Front-fender emblems call out the presence of both the CarbonPro carbon-fiber bed and the Duramax diesel engine.

It’s been noted before but it bears repeating that the Sierra is roomy, exceptionally so as a crew cab. It rides well in everyday commuting, though not best in class, and certainly not with the off-road footwear. The higher-end infotainment system in the AT4 is thorough, but packed with functions that will require some time to gain familiarity. Personal-item storage in the test truck was ample. For instance, it was one of the Sierra models that includes portions of the rear seat back that pull open to expose discrete cubbies.

GMC has fulfilled its promise of a 6-cylinder diesel option for the Sierra 1500. With or without it, the current Sierra holds the promise of good pickup value.

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2020 Sierra Diesel, GMC Sierra 1500 AT4
The Duramax diesel six is a a welcome addition to the GMC Sierra’s (and Chevrolet Silverado’s) powertrain menu for 2020. It helps keep these General Motors trucks competitive with their Ford F-150 and Ram 1500 rivals.

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GMC Sierra 1500 AT4 Diesel Gallery

GMC Sierra 1500 AT4 Diesel

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