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

2020 Sierra 1500 Duramax Towing A Box Trailer

Cars.com photos by Aaron Bragman

By Aaron Bragman

Within one week of each other, both Ram and GMC launched their latest light-duty diesel pickups at media drive events: the 2020 GMC Sierra 1500 Duramax diesel and the 2020 Ram 1500 EcoDiesel]. First, I drove the Ram in Duluth, Minn., towing 7,000 pounds worth of boat trailer at highway speeds up a respectable 4 percent grade; I drove the diesel in a base model Tradesman, loaded Limited and an off-road ready Rebel. I came away mightily impressed with the Ram EcoDiesel, thanks to its impressive capabilities, stellar interior and smooth operation.

Related: 2020 GMC Sierra 2500 AT4: The Power Wagon for Towing

Then, I headed to Jackson Hole, Wyo., where I did the same kind of activities during our first drive of the new 2020 GMC Sierra 1500 Duramax diesel. (Per our ethics policy, PickupTrucks.com pays for its own lodging and airfare at such automaker-sponsored events.) I stormed around off-road courses in the new AT4 trim and towed an 8,000-pound box trailer up a 6 percent grade at 6,000 feet of elevation with a top Denali trim model. It was an excellent opportunity to compare the two trucks working in similar ways. So how do they stack up, and what about the Chevrolet Silverado 1500 Duramax?

Efficient, but Not as Much as Chevy

When I drove the new 2020 Chevrolet Silverado 1500 Duramax diesel earlier this year, Chevrolet didn't offer any towing or off-roading opportunities, just on-road fuel economy loops. GMC decided to take care of that with the launch of its version of the truck. We won't go into the street performance of the Duramax light-duty model because it's pretty well been covered in the Chevrolet's first drive. Suffice it to say that the GMC isn't all that different in how it behaves on-road — it's quiet, smooth, and rides and handles pretty much just like the Silverado.

What the GMC doesn't do is match the Chevy's fuel economy numbers — the best the Sierra manages is an EPA-rated 23/30/26 mpg city/highway/combined for a rear-wheel-drive model, while the best Chevrolet model achieves 23/33/27 mpg. GMC engineers say the different aerodynamics and weight of the Sierra are the cause of the disparity. So if you're looking to maximize fuel economy, you'll want to opt for the Chevy, but if luxury appointments and more conservative styling are instead your jam, the GMC isn't exactly a fuel hog.

How Does Sierra Duramax MPG Compare to Ram EcoDiesel MPG?

We don't know yet — Ram hasn't released EPA ratings for the 1500 EcoDiesel as of this writing. But given that the Chevy's overserved fuel economy in my testing bested the Ram in our brief first drives by a considerable margin, and the GM trucks have 10-speed transmissions versus the Ram's eight-speed, it might be hard for Ram to catch the GM duo on efficiency.

Off-Road: Are Sierra and Ram Diesels Comparable?

2020 GMC Sierra 1500 AT4 Duramax Rock Climbing

Unlike the Silverado, you can get the new light-duty diesel in the Sierra 1500's AT4 off-road trim — the mechanically similar Silverado 1500 Trail Boss model is not available with a diesel. On the GMC, the AT4 brings a 2-inch lift kit, Rancho monotube off-road shock absorbers, four-wheel drive with automatic locking rear differential, extra skid plates, 18-inch wheels with optional 20-inchers, and some unique interior and exterior styling. It's pretty comparable to the Ram 1500 Rebel trim with a few exceptions: Ram adds a manually lockable rear differential, an optional air suspension and a more complete redo of the interior than the Sierra has with the AT4 trim. And now for 2020, both of these trucks can be had with a diesel engine — the Ram's turbocharged 3.0-liter V-6 EcoDiesel makes 260 horsepower and 480 pounds-feet of torque, and the Sierra's turbocharged 3.0-liter inline-six-cylinder Duramax pumps out 277 hp and 460 pounds-feet of torque.

2020 GMC Sierra 1500 AT4 Off-Road

I noted in my review of the Ram Rebel EcoDiesel that the biggest challenge in driving it off-road was modulating the throttle, besotted as it was with turbo lag. In the dirt, the Sierra AT4 diesel feels almost exactly the same. Like the Rebel, the GMC AT4 diesel crawls up and down obstacles with ease, featuring sufficient clearance underneath to get over sharp objects and extra protection for the moments that it can't. Crawling in the Sierra AT4 is simple thanks to its Traction Select System and two-speed transfer case. Just flip a few knobs and the Sierra will do what's asked of it. The limited off-road course GMC provided didn't challenge the big truck all that much, but it felt surefooted, solid and offered something I've yet to experience in a Ram Rebel: a forward-facing trail camera, invaluable for seeing what's over the next ridge when your nose is in the air (Ram insists that it's coming).

2020 GMC Sierra 1500 AT4 In Mud

At higher speeds and higher rpm the Sierra's Duramax engine is less happy. I got bogged down in some deep mud by not having enough throttle going into the muck, and I was not able to bring the revs up while I was in it. A second attempt at crossing some deep mud at higher speed was more successful. While doing some moderate speed two-track driving, the Rancho monotube shocks and greater suspension travel of the AT4 were quite at home, delivering a surprisingly smooth ride over rough terrain. The AT4 equals the Ram Rebel is many ways in terms of capabilities when the pavement ends.

GMC: Tows Like a Champ

2020 GMC Sierra 1500 Denali Towing Box Trailer

The other area where the Sierra 1500 Duramax matches up well with the Ram 1500 EcoDiesel is in towing abilities. Being diesel engines, they're made for this kind of duty, but you wouldn't know it from the tow ratings, which don't differ that much from the regular gas engine options in these trucks. The Sierra 1500 Duramax can be optioned to tow a maximum of 9,100 pounds, while the Ram comes in at a much higher 12,560 pounds — a frankly silly number, given that anyone towing a trailer that heavy has almost certainly traded up for a heavy-duty pickup, which is much better suited to towing such heavy loads. The Sierra's gasoline version can tow a maximum of 12,200 pounds, while the Ram's gasoline maximum is 12,750 pounds. But light-duty diesel trucks aren't really about how much you can tow, they're instead more about how much better you can tow. And both the Sierra and the Ram diesels tow much better than their gasoline counterparts.

With a Sierra 1500 Denali Duramax, I towed an 8,000-pound box trailer up some 6 percent mountain grades at more than 6,000 feet of elevation, a challenging setup for a light-duty truck, and came away mightily impressed. The new baby Duramax is simply a fantastic motor for towing, and the Sierra wasn't bothered at all by the heavy load being dragged from the bumper. The truck was confident and relaxed, making towing almost a nonevent. The transmission performance was top-notch, with the 10-speed automatic well matched to the diesel engine's capabilities. Braking performance was excellent, and the truck never felt like it was being pushed around by the trailer. Engine braking is available, but there's no switch to activate it as it comes on automatically only when cruise control is engaged.

Perhaps best of all is the presence of GMC's ProGrade Trailering system in the Denali, which adds up to 15 camera angles with the use of accessory cameras, enabling the magical "invisible trailer" mode. So not only does the truck tow beautifully — when you look at the display screen to see the trailer behind you, it shows you the view behind the trailer instead. It switches views based on your steering angle and turn signals as well, so you can see into the blind spots down the side of the truck and trailer.

The Ram tows quite strongly as well, but I wasn't able to test it at quite the same grade, trailer weight or elevation as the Sierra. That will have to wait for a later test, but both of these trucks acquitted themselves admirably, making the idea of spending a little extra coin on the diesel option less of a hard pill to swallow. Presumably, both trucks should also get superior fuel economy while towing these loads, but that too must wait for a better, longer, instrumented test.

Which to Choose?

From a capability standpoint, both the new Sierra 1500 Duramax and the Ram 1500 EcoDiesel are well matched. The optional diesel engine costs are even similar as well, with the Sierra charging $2,495 more than the optional 5.3-liter V-8 and $3,890 more than the standard turbocharged 2.7-liter four-cylinder engine. The Ram diesel will set you back $4,995, or $3,000 more than the optional 5.7-liter Hemi V-8 engine. Since GMC has not yet released pricing for the 2020 Sierra 1500, we can't comment on how the Sierra stacks up trim by trim with the Ram in terms of pricing.

2020 GMC Sierra 1500 Side Profile

But capability and option pricing is largely where GMC ends its comparability with the Ram EcoDiesel. When it comes down to cabin quality, amenities and ride refinement, the Ram walks away the clear winner. Comparing the unremarkable interior of a top-of-the-line Sierra 1500 Denali with the absolutely jaw-droppingly opulent cabin of a Ram 1500 Laramie Longhorn is almost embarrassing. The Ram feels like it's in another class altogether, and actually worth its shockingly high sticker price. The Sierra does not; while the AT4 interior has some fun upholstery with its Kalahari brown leather seat accents, the Ram Rebel has a more unique style to it and far better material quality. The availability of the Ram's 12-inch vertical touchscreen is also a factor, but that's negated in its uniqueness by the Sierra's outstanding head-up display, superior trailer towing electronics and some new bed technology like the availability of a seemingly indestructible carbon fiber bed and the slick new MultiPro tailgate.

It seems that once again, GM engineers have delivered a fantastic truck that's let down by its disappointing interior. If that's less of a factor for you, the new GMC Sierra 1500 Duramax delivers solidly on the factors that GM says matter to its buyers: capability, durability and reliability, and now featuring improved efficiency as well.

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