2021 GMC Sierra HD Denali Diesel: Big Boys Only Good if They Work Every Day

2021 GMC Sierra 2500 HD Denali Photo Credit GMC

2021 GMC Sierra HD Denali Diesel Review

By Bill Owney

DALLAS – More than two years later, I was finally heading to a favorite diversion, the Dallas Auto Show.

Yes, I love looking at things that are beautiful and shiny.

COVID changed so much. New cars cost more than $45,000, used ones more than $30,000, and people wait weeks to get them. The conclave of cars and pickups at the convention center on Griffin Street in downtown Dallas is now called the North Texas Auto Show, and a third of the cavernous hall was empty, the space filled with miniature tours of a handful of charming-looking electric vehicles. but far from ready to conquer the planet.

One thing remained the same, my luck. This was one of those weeks where I didn’t know what I was driving until I looked out the dining room window – kind of like a kid on Christmas morning – to see what car the elves have delivered.

Two days before my trip to big D, a shiny and black, $70,000 plus, diesel-sucking, huge pickup, a 2021 GMC Sierra HD Denali 2500, plopped into my driveway like the Pillsbury Dough Boy trying to fit into a Little Ducky inner tube .

Powered by a 6.6L V-8 Duramax turbodiesel bolted to an industrial-grade 10-speed Allison automatic, this beast pumps out 445 hp, 910 lb-ft of torque and can tow 18,510 lbs. behind it.

Heck, and I left my cabin cruiser in my second garage.

But those diesel prices

As amazing as these numbers may seem, more important, from my perspective, was this number: $5,094. That was the price of a single gallon of diesel in Texarkana the day I traveled to Dallas.

A little running of errands showed the Black Behemoth getting 12.2 mpg in the city. I dug a little deeper into the onboard fuel monitor and found that it had averaged 15.5 mpg over the previous 1,657 miles. It would have to go better than that if we were to put in 370 miles round trip and then get through the remaining five days of the week.

Filling up a 36-gallon fuel tank at $5 per was NOT on Dad’s agenda. It’s enough that he had to take a day off, eat on the road and pay for a hotel. (Sleep, one of these micro-hotels is a quiet, clean place if you’re comfortable sleeping in a walk-in closet. Price: $112, plus $12 parking.) Sigh — you guess there are more expensive hobbies.

A radical experiment = 8.4% improvement

On the way back and forth I tried something radical. I drove Below the speed limit. Stop screaming. The world is not ending. It just stopped spinning, for a day or two. No doubt the idea that you were really going 73 in a 75 had a negative cosmic pull and likely delayed spring by a week or so, but we all seem to have survived.

The net effect was that fuel economy improved to 16.8 mpg—an 8.4% increase—and I was able to drive round trip to Dallas, come home, grocery shop, go to work, and even make a weekend run to the lake, and the little orange fuel light didn’t come on until the morning the nice man came to retrieve his big old truck.

Of course, it cost General Motors $180 to get him back to Dallas. Plus, DEF, the expensive fluid that has to go in diesel tanks with some tanks, was getting low.

To be honest, that little voice in the back of my head tells me I should have driven my Highlander Hybrid to the capital D. Not only would it have gotten twice the fuel economy, albeit on my dime, but diesels also put out 25 to 400 times more mass of particulate black carbon and miscellaneous organic matter per mile; so it was a lot of pollution to pour into the atmosphere just for the privilege of sitting up high and acting like I was somebody important.

Nice enough

2020 GMC Sierra HD Denali interior
2021 GMC Sierra HD Denali Photo Credit GMC

That leads to the only compelling point I’m likely to make today. These heavy-duty pickups only make sense if you’re towing something massive daily and weekly, and not just because they’re bouncy and uncomfortable but something heavy in the back. Today’s quarter-ton pickups have plenty of pulling power and much better fuel economy.

GMC’s Duramax diesel will tow 18,500 lbs. Ford’s F-2550 diesel will tow 22,800 pounds. and the Ram’s 6.7-L Cummins® Turbodiesel will pull 20,000. Those are big numbers. A four-horse trailer, on the other hand, weighs anywhere from 4,200-8,400 pounds. Add four horses up to 660 lbs. per, and the weight is still less than the capacity of a competent quarter-ton truck.

Surprisingly, GM’s 3.0-L Duramax only tows 9,500 pounds, but both Ford and Ram offer quarter-ton diesels that tow more than 12,500 pounds. Fords get you about 27 mpg and Rams more than 30 mpg.

Is efficiency possible in this category…

Motor Trend has a nice recap of these questions. I’ve been looking at payload and towing capacity charts for more than four decades and this year I found the biggest surprise yet. Both the Ford and Toyota manage to tow more than 12,000 pounds. combine hybrid systems with twin-turbo V-6 lineups. My friend Tim Esterdahl, a pickup expert, thinks the new Tundra has the best fuel economy of any light pickup ever.

Beyond that, the GMC Denali still leaves a lot to be desired. While it has plenty of nice features, including a camera system that finally rivals Ford’s, the interior still has a cheap and plastic feel. Still, it has plenty of storage, cubbyholes, drink holders and electrical outlets. Pickup drivers, who tend to prefer practicality and versatility over aesthetics, will find it sufficient.

An available 8-inch infotainment screen is notably smaller than the 12-inch screens available on the Ram for two years.

In addition, key pieces of driver assistance technology are not available. I understand that pickup drivers tend to be conservative and therefore the demand is probably not high, but a truck’s ability to stay in its lane and a safe distance behind the vehicle in front seems more important when towing 10 tons from the rear.

Who buys a vehicle for $70,000? Financial advisors say a car purchase should be no more than 35% of gross income. Let’s see … 0.35X = $70,000. Divide both sides by 0.35. Oh, that’s $200,000 a year right? Less than 7% of the American public does.

You would think that the top 7% would be more discerning.

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