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2020 GMC Sierra 1500 Diesel review: Silent strongman

The combination of off-road-ready parts and one seriously strong diesel engine make for quite the light-duty pickup.

Andrew Krok Reviews Editor / Cars
Cars are Andrew's jam, as is strawberry. After spending years as a regular ol' car fanatic, he started working his way through the echelons of the automotive industry, starting out as social-media director of a small European-focused garage outside of Chicago. From there, he moved to the editorial side, penning several written features in Total 911 Magazine before becoming a full-time auto writer, first for a local Chicago outlet and then for CNET Cars.
Andrew Krok
6 min read
2020 GMC Sierra 1500 Diesel
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2020 GMC Sierra 1500 Diesel

That's one mean-lookin' pickup.

Andrew Krok/Roadshow

I'm not going to pretend like I needed an entire 2020 GMC Sierra 1500 to move 1 cubic yard of mulch, but things just worked out that way. Over the course of a week of light garden work, I found out that there's a whole lot to appreciate in this pickup. It's not perfect, but GMC's new Sierra is still quite compelling.

8.5

2020 GMC Sierra 1500 Diesel

Like

  • Blessed powertrain
  • Decent economy
  • Solid consumer tech

Don't like

  • Loud, meandering off-road tires
  • Already-aged interior design

AT4 package brings the looks

If the standard is already overkill for moving a couple hundred pounds of processed tree bark, my tester's AT4 trim definitely ramps up the excess. Meant to give the Sierra a bit more off-road cred, it jacks the body to the sky with a 2-inch lift, supported by Rancho monotube shocks, skid plates, a locking rear differential, chunky Goodyear Wrangler Duratrac tires, red tow hooks, a spray-on bedliner and AT4 badges all over the dang place. It makes an impression, too; I don't usually get compliments from strangers when driving pickups, but this one earned a few positive comments in the Target parking lot.

It definitely makes the truck look more badass, but the AT4 trim is a pricey proposition. In my tester's layout (crew cab, short box), a base Sierra 1500 4WD will set a buyer back about $40,000, but the AT4 is the trim just below the top-tier , so the price rises to about $54,000.

2020 GMC Sierra 1500 Diesel
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2020 GMC Sierra 1500 Diesel

It's a little old, and the button layout is a little dense, but the Sierra's cabin remains usable and, in my tester's trim, plenty comfortable.

Andrew Krok/Roadshow

The interior leaves me wanting more, though. GM got raked over the coals, and rightfully so, when the new Chevy Silverado and GMC Sierra debuted. For as new as the exteriors were at the time, the interiors received little in the way of aesthetic updates. With the exception of some general rearrangements, the Sierra 1500's innards are nearly the same as before. The center of the dashboard is kind of this hot mess of switches that will take some getting used to. While the screen in the gauge cluster did grow a bit, the physical gauges still use the same fonts and designs from over a decade ago. I understand that pickup buyers may be more hesitant about change than, say, a Hyundai Elantra owner, but still. Things look a little more dire when you see what Ford has in store for the 2021 F-150, too.

That's not to say the interior doesn't have plenty of redeeming qualities, though. My AT4 tester has some seriously comfortable leather seats, and the dashboard is well trimmed with the soft stuff, too. Dual-zone climate control is standard, as are 10-way power front seats with heating and ventilation, as well as a heated, leather-wrapped steering wheel. It's not Denali-cushy, but it's pretty darn close. There's also more space than you can shake a stick at, with the second row feeling positively voluminous. If you need to cram a bunch of junk back there, the rear seats fold up and out of the way with ease.

Mulch master

There aren't too many opportunities to really dig into the Sierra 1500's raw capability here in metro Detroit -- I don't own a boat, nor a contracting business, nor horses -- so I was happy to haul about a cubic yard of mulch back from the garden center. Since I'm not exactly Ron Swanson, the most useful tool I have for moving mulch from truck to garden is an aluminum snow shovel, which picks up the stuff without leaving so much as a single scrape in the standard spray-on bedliner. I was worried that I'd created one hell of a mess, but I found I was able to get the bed back to mostly-clean status with just a broom and a leaf blower. A quick trip to the local car wash and its high-pressure hoses brought the bed back to sparkling.

Generally, it's pretty easy to feel the difference between an empty truck and one that's got a sizable amount of stuff in tow (or in the bed), but the Sierra 1500 AT4 offers surprising amounts of cushion at all times. Unladen trucks can occasionally be a mess on the road, bouncing over expansion joints and generally being quick to unsettle, but I'm plenty comfortable no matter what I'm up to in the Sierra. The steering is on the light side, but pedal modulation is ace. The only real annoyance comes by way of the 275/65R18 Goodyear Wrangler off-road tires, which make tons of noise and occasionally cause the truck to wander at lower speeds around town. Sure, they complete the look, but at what cost?

2020 GMC Sierra 1500 Diesel is a hauling pro

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Available on all but the base trims is a new 3.0-liter Duramax diesel inline-six. Producing 277 horsepower and 460 pound-feet of torque, it's enough for a tow rating of 9,100 pounds and a payload rating of 1,830 pounds. That's a little lower than the competition's diesel offerings, but as Roadshow's Emme Hall pointed out in her first drive, GM found that most of its customers looking to tow five-digit loads would just buy a heavy-duty truck instead.  

Combined with a 10-speed automatic transmission, the Sierra 1500's new diesel engine is surprisingly sedate. The usual lug-lug-lug idle isn't there, nor does its clamor reach a fever pitch. This straight-six is generally quiet and ready to lay down monster amounts of torque when necessary, meaning the truck actually feels pretty darn quick when it's unladen and I need to slam-a-jam the throttle. It's just as pleasant with a bed full of shredded tree detritus. The 10-speed does a pretty good job of picking the right gear and smoothly making its way there, a nice change of pace from what I experienced with its downshifts when mated to a gas V8.

Since GM assumes 10,000-plus-pound towing aficionados will move toward Sierra 2500s and up, the automaker chose to focus on efficienty with the Sierra 1500 diesel. The EPA rates this four-wheel-drive pickup at 22 miles per gallon city and 26 mpg highway, numbers that I am able to match, and I find myself occasionally squeezing out a couple of extra mpg in the latter scenario.

2020 GMC Sierra 1500 Diesel
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2020 GMC Sierra 1500 Diesel

Aiming for efficiency was the smart move here, since GM knows true tow aficionados will opt for Sierra 2500s and up.

Andrew Krok/Roadshow

Darned good tech

No matter what you're after, whether it's creature comforts, safety or capability, there's a tech package that'll boost the Sierra 1500's credentials. The $2,125 Technology Package adds a higher-definition backup camera, a bed-view camera, a head-up display, a digital rearview mirror and a larger screen in the gauge cluster. On the safety front, a $1,095 package adds automatic emergency braking, adaptive cruise control, lane-keeping assist and a haptic feedback seat cushion -- a surprisingly affordable grouping, given the nickel-and-diming GM likes to do with safety systems in some of its mass-market vehicles.

As with its other new vehicles, GM's infotainment continues to impress here. The Sierra 1500 AT4 comes standard with an 8-inch touchscreen running the automaker's latest software, which is responsive and easy on the eyes, not to mention loaded with fripperies like Apple CarPlay, Android Auto and a 4G LTE Wi-Fi hotspot. A pair of USB ports (one USB-A, one USB-C) is standard in each row. If you want to ramp up the cabin tech further, a $3,355 AT4 Premium Package adds embedded navigation, a power sliding rear window, a wireless device charger, blind-spot monitoring and parking sensors. Tech isn't usually the point of a truck, but props to GMC (and GM in general) for finally bringing its trucks into parity with the rest of its vehicles.

2020 GMC Sierra 1500 Diesel
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2020 GMC Sierra 1500 Diesel

Considering the embiggening of screens in trucks nowadays, the display in the Sierra feels positively tiny.

Andrew Krok/Roadshow

How I'd spec it

My tester is expensive, with the AT4 starting at $53,400 and rising to an out-the-door price of $63,565 including destination after the diesel engine and a few options packages are added. Since I'd prefer fewer off-roady bits, I'd start with the lower SLT trim but retain the smooth diesel I6. I'd drop $7,160 on a massive SLT Premium Plus package that loads the thing up with all the driver-assistance tech and just about all the options found in my AT4 tester. That brings me up to $61,650 including destination, which would save me a couple of grand compared with the truck I'm reviewing.

Down to brass tacks

Do I even need to mention the competition in this segment? It's not like it's changed in… decades. If you want something a little less luxurious but generally the same as the Sierra, opt for the oddly styled Chevy Silverado. If you want to hold out for a hybrid, the 2021 Ford F-150 will scratch that itch, and its complement of consumer tech looks hard to top. The remains our darling, though, with top-tier aesthetics, on-road comfort and capability. There are some also-rans, too, like the and the , but they're hard to recommend over the segment stalwarts and their vast experience in this arena.

The 2020 GMC Sierra 1500 has added a powerful tool to its arsenal: With a smooth-operating, hard-pulling straight-six diesel engine under the hood, the Sierra's capability grows without making sacrifices in daily drivability, and boosts efficiency a bit in the process.

8.5

2020 GMC Sierra 1500 Diesel

Score Breakdown

Performance 8.5Features 8.5Design 8Media 9