Truck King Challenge Winner – Long-Term Test – GMC Sierra 1500

Story and photos by Howard J Elmer, additional photos courtesy of GM Canada

The 2019 GMC Sierra Denali 1500 took the top award at last fall’s Canadian Truck King Challenge. That win, for the GMC half-ton, was a first in the 13-year history of our event. It also came as the Sierra went through a generational update – bringing with it a host of new features, inside and outside the truck. The judges considered everything the new Sierra had to offer, and after two days of intensive road testing, scored it highest among its peers. Testing, as those who follow the Challenge know, includes empty test loops, driving with payload and also towing our low-boy trailers loaded with concrete and having a gross weight of 7,000 lb.

Still, no matter how thorough our testing is, it’s still just a snapshot taken over two days, so considering that Truck King is known for doing real-world testing for Canadians, we felt we could do better.

So, with the assistance of GM, we have our 2019 winner back for four months of additional road test time. This is the same truck we had last fall. At the time it came to us with just 1,000 km on the clock, but since we drove it, it’s been used by other auto journalists regularly, and these writers have added 8,000 kilometres to the odometer.

The Sierra is currently being used as a daily-driver – which includes the regular towing of any of the seven trailers I own. I am driving it, as is my wife, and even my son, auto-journalist Stephen Elmer. My grandson, Otis, is not driving, but getting his car-seat in and out is a story in itself.

My plan for this long-term test is to report the good and the bad as it presents itself during daily operation, while also examining and reporting on the truck’s key features. To that end, we are using the truck as any Canadian would. Luckily, we have started at the tail end of winter and will continue through spring into summer.

I will be writing about my experiences regularly, as well as producing YouTube videos on our Truck King channel, so you can watch me on-line or read my comments on the various components and features of this new Sierra.

Today’s discussion centres on the new powertrain in my Sierra. It was built with the 6.2L V8 gas engine coupled to GM’s 10-speed automatic transmission. This is a new combination and, in my truck, also features a new system from the General called Dynamic Fuel Management.  This industry-first technology enables the engine to operate in 17 different power patterns, all governed by demand.

The first thing to note here is that while there are other “fuel management” systems on the market, as of today, none are as efficient as this one. DFM is the next generation of GM’s other deactivation system; Active Fuel Management. First introduced in 2005, AFM has been in use ever since. This original system fuelled either eight cylinders or four – depending on the power demanded from the engine. A seamless system, it requires no input, or thought for that matter, from the driver.

The point to this system? Well, it’s two-fold. First is the obvious one – it saves fuel. The second reason for its existence is GM’s engineering decision to not go with turbo-chargers on its truck engines. So, instead of lowering displacement and using turbo’s to make up for the drop in horsepower, they have maintained the size of their small-block V8s, but found another way to save fuel. This strategy applies to the two main truck engines on offer – the 5.3L V8 and the 6.2L V8. Now, at this point, I do have to state that GM has dipped its toes into “that” other pond with a 2.7L turbocharged four-cylinder engine. However, that’s a story for another day.

In our test truck, we are running the 6.2L V8 engine. It’s the segment’s largest and most powerful engine – making 420 hp and 460 lb-ft of torque. It uses a cast aluminum block and head. Its valve train is designed with a single camshaft and two overhead valves per cylinder; it features variable valve timing and feeds those cylinders via direct high-pressure fuel injection.

Dynamic Fuel Management is certainly more complex than the earlier AFM system. But that added complexity has resulted in greater gains on the fuel savings side, while still keeping the punch of the V8 available.

GM says that drivers require V8 power less than 40-percent of the time – meaning DFM kicks in and saves the fuel that would otherwise be pouring into unneeded cylinders. This electro-mechanical system can deactivate any of the engine’s 16 hydraulic valve lifters. These two-piece lifters “unlatch” when the solenoid gives the command and keep the ports closed. As to how many are closed – well, that’s determined by the inputs from the accelerator pedal and calculations based on the requested torque. The computer that runs this system can make these calculations (and send commands) as often as 80 times a second.

From my perspective as the driver – after several weeks of operation – I don’t notice any changes in performance while driving. There is no change in sound, or any noticeable “feeling” while driving. In the city or on the highway, there is nothing to indicate that DFM is in operation – it works completely in the background, but when punched, the big V8 delivers power instantly. This invisible effort from DFM is exactly what I want.

As I mentioned earlier, the truck has a 10-speed automatic transmission. Again, fuel savings is a big plus here – if you add gears, you lower power demand particularly from a standing start.   This new transmission was designed for improved shift quality by adding a new centrifugal pendulum absorber torque converter that effectively reduces vibration. This is particularly relevant during cylinder deactivation events – another reason why the DFM is so subtle while operating.

The last piece of this fuel savings effort is the addition of a standard Stop/Start system. These have been around for several years and various fuel studies claim as much as a three-percent  annual savings in fuel – simply by regularly stopping the engine at traffic lights. Still, some folks find it annoying. To that end, there is a centre console toggle switch that shuts it off if you so choose, though you do have to do it each time the truck is re-started, as the system resets itself whenever the engine is shut down. It doesn’t bother me – but it does bug my wife.

As of today, we have added around 3,000 km to the total on the odo, and while we are getting more familiar with the truck, there have been no issues to report.