2020 GMC Sierra 1500 SLT Duramax Review

GMC’s Sierra 1500 was completely redesigned for the 2019 model year, bringing a bold design and useful tech features such as the nifty MultiPro split-opening tailgate. For model year 2020, GMC's updates to its bread-and-butter Sierra 1500 are designed to assist in towing, fuel economy, and commuting.

Some of the enhancements for the 2020 Sierra 1500 include the following:

• Enhanced ProGrade Trailering which adds 15 camera views
• Adaptive cruise control now available
• First full model-year availability of the new 3.0L Duramax turbo-diesel engine

We didn’t have the Enhanced ProGrade Trailering on this particular example, but our tester had the adaptive cruise control and Duramax engine. There are plenty of reviews on the internet regarding the 2019 model year redesign; therefore, we'll focus primarily on the new diesel engine and how it handled everyday life.

Primary Competitors:

• Ford F-150
• Dodge RAM 1500
• Chevrolet Silverado 1500
• Nissan Titan
• Toyota Tundra

Disclosure: General Motors provided a 2020 GMC Sierra 1500 SLT to test out for a week.

Quick specs:

• Starting MSRP excluding destination: 2020 Sierra 1500 2WD Crew Cab SLT $46,700 + SLT Premium Plus Package ($7,210), Duramax Turbo-Diesel ($2,495), Red Quartz Tintcoat ($595), Destination charge ($1,595) and SLT Premium Plus Package Discount (-$1,000)
• As tested price: $57,595
• 3.0L inline-6 cyl turbo-diesel engine 277 horsepower/460 lb-ft torque
• 10-speed automatic transmission
• 275/60R20 all-season tires, 20” polished aluminum wheels
• 1st row/2nd row Headroom (Inches): 43.0/40.1
• 1st row/2nd row Legroom (Inches): 44.5/43.4
• Fuel Tank (Gals): 24.0
• Fuel Economy (City/Highway/Combined): 23/30/26
• NHTSA Overall Safety Rating: 4 Stars

1/4

With its classic proportions, the side profile view of the GMC Sierra 1500 is arguably one of its best angles. (Bestcovery)

2/4

The Duramax badge on the fender is one of the only signs on the truck's exterior that gives away which engine lives under the hood. (Bestcovery)

3/4

The square-jawed theme is echoed throughout the Sierra's overall design, including the trademark wheel arches. Note the cutouts in the rear bumper that allow easy access to the bed. (Bestcovery)

4/4

The MultiPro split-opening tailgate can be identified by its distinctive cut-lines. This feature is unique to the GMC Sierra, and is not (yet) available on the Chevrolet Silverado. (Bestcovery)

The 3.0L inline-6 turbo-diesel Duramax engine was a late-availability option for the 2019 model year, but is readily available on any 2020 Sierra, SLE and up. Our tester was an up-level SLT model with 2WD, but the Duramax engine can also be paired with 4WD on all the trims where it's available. The 3.0L Duramax is a $2,495 option, rated at 277 horsepower and 460 lb-ft torque at low 1,500 RPM. While the horsepower number looks unimpressive on paper, the torque figure actually matches that of the 6.2L V8 and shows up a whole 2,600 RPM earlier. It's definitely got power where it counts, and a Sierra packing the Duramax can tow up to 9,100 pounds when properly equipped. The GMC Sierra is not the only ? ton truck with a 3-liter diesel option, not counting its obvious corporate sibling, the Chevrolet Silverado. FCA has offered a diesel engine for the RAM 1500 since 2014; though the current model initially launched without a diesel engine option, it's available once again for the 2020 model year. The RAM's 3.0-liter turbo-diesel V6 is rated at 260 horsepower and 480 lb-ft torque and can tow up to 12,560 pounds when properly equipped. Ford offers a 3.0-liter turbo-diesel V6 in the F-150 as well; that engine is rated at 250 horsepower and 440 lb-ft torque. When properly equipped, the diesel F-150 can tow up to 11,400 pounds.

1/2

Under the plastic cover lies a brand-new 3.0-liter inline-six engine. Though it's unrelated to the 6.6-liter turbodiesel V8 found in GMC's heavy-duty trucks, the Duramax name is shared to convey its overall capabilities. (Bestcovery)

2/2

The inline-six cylinder configuration brings inherent mechanical balance that eliminates the excessive NVH that older diesel engines are known for. (Bestcovery)

The Sierra 1500 with the Duramax diesel is a breeze to drive. Low end torque is readily available and is all too easy to utilize when merging onto the freeway or passing slower vehicles. The old-school diesel clatter has been banished; instead, it sounds similar to many modern direct-injection gasoline engines at idle. Any hint of an oil-burner residing underneath the hood is almost imperceptible from inside the cabin, with the possible exception of the baritone engine note. The 3.0L Duramax pairs exclusively with the 10-speed automatic transmission that was previously restricted to certain engine options. Though GM and Ford may have co-designed the transmission, each company applies its own tuning characteristics. In the Sierra, shifts were quick and seamless, and downshifts were provided without delay. Despite the presence of 10 forward speeds, there was absolutely zero hunting for gears in any of the driving conditions we threw at the truck.

1/2

According to the trip computer, we averaged 25.4 miles per gallon over nearly 500 miles of mixed driving. (Bestcovery)

2/2

The automatic climate control allows set-it-and-forget-it operation. We didn't notice any significant impact to fuel consumption. (Bestcovery)

One of the main draws of going with the diesel engine in a half-ton pickup is car-like fuel efficiency without sacrificing towing performance. Sticking with 2WD delivers the greatest efficiency with these diesel-powered half-tons. EPA fuel economy estimates peg the Duramax-equipped 2020 Sierra 1500 2WD Crew Cab at 23 city, 30 highway, and 26 combined. Among the competitive set, the RAM is also rated at 26 combined MPG while the Ford is rated slightly lower at 25 combined. The GMC ekes out one more MPG in the city at 23 versus the Ford and RAM; meanwhile, the RAM is the highway king with an estimated 32 MPG on the highway. In 4WD configurations, the Sierra and RAM are both rated at 24 combined with the Ford trailing by 2 MPG. The RAM is the clear winner on the highway again at 29 MPG while the Sierra is rated at 26. In the city, the GMC wins with 22, the RAM at 21, and F-150 at 20, respectively. After almost 500 miles of driving with approximately 70% of those miles on the highway, I averaged 25.4 MPG according to the onboard computer. On paper, it's slightly less than estimates; considering that this is a full-size ? ton truck, these numbers are downright impressive.

1/5

The interior of the 2020 GMC Sierra 1500 SLT is perfectly functional, and the storage options are plentiful and well thought-out. (Bestcovery)

2/5

On the other hand, the materials quality is disappointing. While we're willing to give GMC some leeway, FCA's latest effort in the RAM 1500 proves that pickup trucks and a premium interior are not mutually exclusive concepts. (Bestcovery)

3/5

The front seats are supportive and provide excellent long-haul comfort. One of the biggest improvements is also the most subtle - unlike previous generations of the Sierra, the driver seat and steering wheel are finally aligned. (Bestcovery)

4/5

The rear seat area is also very spacious, and the seats can be lifted for extra cargo space. ()

5/5

In our test vehicle, the outboard rear seats were fitted with 3-stage heating. Note the USB-C charging port placed next to the USB-A port; the square cover to the right conceals a 12-volt outlet. (Bestcovery)

Due to the nature of commuting in Los Angeles traffic, I had no shortage of time to spend with the GMC. The Sierra rode smoothly over freeway expansion joints and didn’t exhibit the usual jouncing associated with body-on-frame trucks - even with the upgraded 20” wheels. The cabin was impressively hushed whether navigating city streets or cruising at freeway speeds; the small amounts of noise that filtered through were easily drowned out by the excellent Bose sound system. The heated and ventilated seats and heated steering wheel were a welcome addition, even in the famously mild Southern California climate. Unfortunately, the abundance of hard plastics and cheesy-feeling buttons made the cabin feel decidedly less premium. The material choices would be understandable given that it's a truck and not a luxury car, but the near $60k price tag of our SLT tester definitely sets expectations that the interior simply can't meet. The other complication is the simple fact that the RAM 1500 exists; FCA has clearly done their homework with interior quality, both perceived and real. We really hope GM will address the subpar interior quality in the truck's mid-cycle refresh.

1/5

The leather-wrapped steering wheel features a plethora of buttons; the left spoke houses the cruise control functions while the right spoke controls the screen in the gauge cluster. (Bestcovery)

2/5

The button with the "crashing cars" symbol adjusts the sensitivity of the forward collision warning system. The button directly below toggles the heated steering wheel on and off; we appreciated the fact that it's in a logical place and provides at-a-glance confirmation. (Bestcovery)

3/5

The MultiPro tailgate can be opened in multiple configurations. The top section of the tailgate can be dropped to access items in the bed or let longer items through without requiring driving with the tailgate down. It can also be used as a table in a pinch. (Bestcovery)

4/5

The "floor" can be flipped up as well, and provides a slight extension to the length of the bed. (Bestcovery)

5/5

Alternatively, the "floor" panel can be opened with the tailgate fully lowered to act more like a traditional bed extender. (Bestcovery)

On the other hand, we appreciate the abundance of safety features. Our tester was equipped with the SLT Premium Plus Package, adding front and rear park assist and a slew of driver assist features. All the usual suspects are present - blind spot warning with lane change alert, lane keep assist, lane departure warning, and automatic emergency braking with pedestrian detection. The rear-view camera also incorporated cross traffic alert, which is especially helpful given the size of the truck. GM's unique safety alert seat provides an alternative to the annoying beeps and dings that normally accompany these systems; a set of haptic "buzzers" are built into the lower cushion of the driver seat and will subtly provide feedback if attention is needed. Another welcome addition is adaptive cruise control, which marks the first time we've seen this feature on a full-size GM pickup truck. It's one of the more traffic-friendly systems on the market, as it can bring the vehicle to a complete stop. We did notice that the system was a little jumpier than we'd like when sitting through one of LA's notoriously obnoxious traffic jams, and it often left enough space for more impatient drivers to cut in front. That said, I did appreciate that fact that the truck remembered the desired following distance setting even if you turned off the adaptive cruise and turned it back on.

The 2020 GMC Sierra 1500’s diesel engine clearly makes a case for itself, and is good enough to make up for the truck's other shortcomings. Given the smooth operation and high average MPG of the Duramax/10-speed pairing, it is an easy vehicle to live with on a daily basis. The numerous driver aids make it a cinch to drive and park, and the fact that the adaptive cruise control can bring the truck to a complete stop means the Sierra is a great choice for commuters. Given the negative press from the past several years surrounding diesel engines and emissions, the toughest part for GMC is convincing skeptics who would otherwise find that the Duramax is a perfect fit.