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2020 GMC Sierra AT4: Diesel power plus off-road prowess?

2020 GMC Sierra AT4 Duramax Review

The front end for the 2020 GMC Sierra is a great look without being polarizing. (Photo by Tim Esterdahl)

While the Ram TRX and Ford Raptor still get most the attention among truck fans, the 2020 GMC Sierra AT4 is really hitting the sweet spot of adding off-road ability to a stock pickup for most consumers. Plus, the availability of the 3.0-liter Duramax diesel gives you the all-important low-end torque.

A week behind the wheel confirmed the obvious: This truck is really, really good, and the price is really, really high.

The recently updated GMC Sierra AT4 has been seen as the more attractive option for many truck fans dropping the very polarizing Chevy Silverado front end for a more attractive-for-all front grille design.

2020 GMC Sierra AT4 Duramax Diesel

Unique styling cues on the 2020 GMC Sierra AT4 include having the Sierra spelled out on the headlight. (Photo by Tim Esterdahl)

Beyond the grille, designers included several unique touches like adding the “Sierra” name to the headlights, putting in air passages around the front of the wheel well to allow for better aerodynamics and vertical, red tow hooks which still managed to stand out on our test model’s Red Quartz Tintcoat exterior color.

What is the AT4 Package?

Adding to the larger truck look is the AT4 package with its 2-inch factory-installed lift, 18-inch wheels, skid plates, unique machine-face, dark-tinted wheels, black chrome finish on the fog lamp bezels, fender surround and grille insert and body-color grille surrounds, door handles and bumper. Plus, it adds the MultiPro tailgate (now found on the Chevy Silverado).

Besides the look, the AT4 package adds hill descent control (low-speed, cruise control like system), traction select system, interior accents like AT4 stitched on head rests.

Our test model also had the $3,355 AT4 Premium package, which added a universal home remote, rear sliding power window, premium infotainment system (8-inch screen, bluetooth audio streaming, Apple CarPlay, Android Auto), Bose premium sound system, wireless phone charging, front/rear park assist, lane change alert with side blind zone alert, rear cross-traffic alert, 6-inch black rectangular assist steps and Goodyear Wrangler Duratrac tires.

In other word, it had every bell and whistle you could imagine you needed or didn’t need.

Putting all of these features and equipment into use translated into a much taller, more capable and more pleasurable driving experience than a stock GMC Sierra 1500.

That’s not all, though. The 3.0-liter Duramax diesel is really something as well.

Finally half-ton diesel power!

2020 GMC Sierra 3.0L Duramax diesel

A “clean sheet’ design, the 3.0-liter Duramax diesel was built for GM body-on-frame trucks like the Sierra. (Photo by Tim Esterdahl)

For the last decade or so, truck fans have been clamoring for a half-ton truck with a diesel engine. Automakers provided these kinds of engines back in the ’80s and ’90s, yet they made a departure due to rising emissions requirements and decreasing customer demand. Now, with astonishing fuel economy improvements, the invention of diesel exhaust fluid and improvements in emissions equipment, they are back — and boy are they good.

This 3.0-liter Duramax diesel, a $2,495 upgrade for 2020 (just $995 for 2021) more than the 5.3-liter V-8, seems perfectly suited for a half-ton truck. It is an inline-six diesel, meaning it is inherently balanced and provides amazing off-the-line performance with 460 pound-feet of torque at just 1,500 RPM! While the 277 horsepower at 3,750 RPM isn’t too shabby neither, the real story is reaching max torque at those low RPMs.

Basically, this low-end torque means you can burn rubber or throw dirt more often and, frankly, more unintentionally than you might like. It also helps with towing upwards of 9,000 pounds by getting the load going quicker and more confidently thanks to the 10-speed automatic with tow/haul mode engaged (exhaust brake automatically engaged as well).

This isn’t to say this engine and truck should be considered a smaller version of a heavy-duty diesel. The 6.6-liter Duramax diesel found in the 2500/3500 models is like comparing a baseball with a beach ball. This smaller diesel can tow pretty confidently, but this smaller displacement engine is really about fuel economy as well.

Plus, payload is rather low with a 1,405-pound capacity on our test model versus the 1,814 pounds for the stock 5.3-liter V-8. This really means you need to pay more attention not only to how much you are towing but also how much you are hauling versus a HD truck.

Our test model was EPA rated at 22/26/24 mpg city/highway/combined. These are pretty good fuel economy numbers — and easy to achieve, especially compared with the 16/22/19 mpg city/highway/combined from the stock 5.3-liter V-8 for the AT4 package.

One last thing about the diesel is while it is a blast to drive, the towing experience is better and the fuel economy is improved over the 5.3-liter V-8, half-ton diesels rarely “pencil out” when you work out the yearly savings versus the upcharge for the engine and the associated costs. However, if you do tow often and enjoy skipping the gas station, those factors need to be included in your cost analysis.

What about the 2020 GMC Sierra AT4 interior?

2020 GMC Sierra AT4 interior

While not much has changed to the naked eye for the 2020 GMC Sierra AT4 interior, there are subtle changes from the prior gens from 2013-2018. (Photo by Tim Esterdahl)

If you have followed trucks for the past two years, you have heard one consistent theme with GM trucks — the interior is blah. This is, without question, true, but also only true to a certain extent.

The reality is GM designers did make changes to the interiors of the 2019 models, however, these changes were slight and most owners will see this interior as being identical to the prior model years of GM trucks. On one hand, this is a good thing since familiarity with the interior means less hassle for new owners trying to find things. On the other hand, for new buyers to the brand, it is hard to see many consumers opting for this interior versus competitors such as the new Ram 1500.

GM’s argument has long been function over form meaning the interior is functional and this matters more than how it looks. While this argument does have its merits, the reality is having a good looking truck inside and outside is important since you will be spending upwards of $60k for our test truck.

The bottom line on the GMC Sierra AT4

2020 GMC Sierra AT4 Duramax diesel

The exterior has the simple to use corner step, dual integrated exhaust and the multi-pro tailgate. (Photo by Tim Esterdahl)

This truck is a winner, and customers are now flocking to the GMC Sierra more than ever before — even with COVID-19 taking a bite out of sales numbers.

The brand growing faster than all full-size trucks, and it’s easy to see why. The handy MultiPro tailgate helps access to bed for many owners, the front end is appealing, the Duramax diesel is available with the AT4 package (Silverado doesn’t offer this), and the truck has excellent ride comfort plus performance.

All this adds up to a good truck on and off road.

Granted, you pay for “all this” with its $64,180 MSRP, and that’s a tough price to wrap your head around for a half-ton truck.

Related posts:

2021 GMC Sierra ups its towing game for 2021 with new tech, equipment

2019 GMC Sierra AT4 1500 Unleashed – Luxury Off-Roading Pickup

Chevrolet flexes its tailgate muscle with Multi-Flex

2020 Ram Rebel EcoDiesel: Rugged looks, everyday-drive temperament


Tim Esterdahl

Automotive Journalist Tim Esterdahl has been a lover of trucks and SUVs for years. He has covered the industry since 2011 and has pieces in many national magazines and newspapers. In his spare time, he is often found tinkering on his '62 C10 pickup, playing golf, going hunting and hanging out with his wife and kids in Nebraska.

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