In 2008, the GMC Yukon Hybrid, and its counterpart the Chevrolet Tahoe Hybrid were the first vehicles to utilize the advanced two-mode hybrid powertrain developed jointly by General Motors, BMW and the then DaimlerChrysler. These full-size sport-utility vehicles launched a new breed of larger people carriers that were significantly greener than their gas-powered versions.

How much greener? Well, we’re not talking hybrid car fuel economy numbers, but the two-mode technology results in a 25-percent improvement in overall fuel economy over the Yukon hybrid’s gas-powered counterpart. More impressive is a 40-percent improvement in city driving. Both the Yukon Hybrid two- and four-wheel drive models have an EPA rating of 20 city/23 highway/21 combined as compared to the conventional Yukon’s 14/18/16 with the 6.2-liter V-8. Unbelievably, this huge SUV’s city fuel economy is 3 mpg better than a Honda Accord coupe with a 3.5-liter V-6 engine and manual transmission.

Automobile Magazine gave the Yukon Hybrid high praise, stating, “We’ve professed our admiration for GM’s two-mode system before, even going so far as to name it our Technology of the Year in 2008. There’s no doubt that it’s a boon for those who seriously need a full-size vehicle–it helps allow an automobile that can seat the Brady Bunch, pull a boat, and return some impressive fuel-economy numbers while driving around town.”

Available with either two- or four-wheel drive, there are two trim levels available. The standard 2013 Yukon Hybrid has a starting price of $52,820 for the 2WD model, $55,630 for the 4WD. The lavishly appointed Yukon Denali Hybrid 2WD starts at $60,635, the 4WD at $63,480. All prices are a $350 increase over the outgoing models, and there are no significant changes for the model-year 2013.

Hybrid Powertrain Details

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GM’s electrically variable transmission (EVT) and 300-volt nickel-metal hydride battery pack work with the standard 6.0-liter V-8 gasoline engine to enable the Yukon Hybrid’s efficient performance. Most of the fuel economy gains come from the (EVT). The transmission is made up of two 60-kilowatt electric motors, three planetary gearsets and four fixed gears that use the same space as GM’s six-speed automatic transmission.

In order to keep the vehicle running at peak efficiency, this hybrid system is able to run in one of two separate modes – hence the name “two-mode hybrid.” For low-speed, low-impact driving, the powertrain works just like other hybrids; during stop-and-go and city drives, the Yukon can operate with electric power only, gas engine power only or a combination of both. Additionally, the engine shuts off when the vehicle stops, and when its time to go, the electric motors propel the big SUV to around 30 mph for a couple of miles.

The second mode is mostly for highway driving, at which time one or both electric motors can run concurrently along with the V8 engine in order to provide a power boost. The two-mode transmission is the key to the whole system, which attempts to keep the engine running at the optimum rpm for low fuel consumption. Essentially, it manages a balancing act between the engine and the electric motors. It is also responsible for making the transitions between the two modes practically seamless.

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The gasoline engine also plays a role in fuel efficiency. For starters, engineers adapted the V8 to operate with late intake valve closing (Atkinson-cycle combustion process) for fuel economy gains. The engine also features cylinder deactivation technology. In other words, this engine can shut down four of its eight cylinders when additional power is not needed – a big fuel saver on the highway.

Despite its focus on fuel-efficiency, the Yukon Hybrid still delivers all the power and capability needed from a full-size SUV. It boasts 332 horsepower, and the 2WD model can tow up to 6,200 pounds, 6,000 pounds for 4-WD versions. If you need it, the four-wheel drive system is comparable to most trail-rated pickup trucks, allowing the Yukon to drive off-road or through difficult road conditions with excellent traction and stability.

Exterior And Interior

Now in its fifth year, the GMC Yukon Hybrid remains a handsome vehicle, with pleasing proportions and a minimum of unnecessary adornment. Slight exterior changes make the hybrid version more aerodynamic compared with the conventional Yukon. A redesigned bumper eliminates the regular Yukon’s fog lights for some corpulent bodywork, including a wider front air dam that moves more air underneath. Also, roof rack rails are eliminated for reduced drag, runningboards are tapered front and rear to decrease wind resistance and the body shape was given sharper cuts to hold air while an extended rear spoiler contributes to the vehicle’s overall aerodynamic performance. The final touch is aero-efficient 18-inch cast aluminum wheels.

The Denali hybrid version is identifiable by its signature chrome honeycomb grille, monochromatic exterior appointments and 22-inch chrome wheels. Interesting that the Denali is missing the functional cosmetic changes made to the regular Yukon Hybrid yet, has the same fuel economy ratings.

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When introduced, the Yukon Hybrid’s cabin set the standard with a straightforward design accompanied by quality materials and craftsmanship. But five years later, competitors have upped the ante. That aside, the list of standard features is quite long including: tri-zone automatic climate control; 12-way power adjustable, heated front bucket seats; Bose sound system; CD/MP3 player; Bluetooth connectivity; navigation system; and power-adjustable pedals. Stepping up to the Yukon Denali Hybrid adds GM’s Magnetic Ride Control, a power liftgate, steering wheel mounted audio controls, heated second row seats and side blind-zone alert.

Behind the 50/50-split third-row seats is a meager 16.3 cubic feet of cargo space. This opens up to 60.3 cubic feet with the third-row seats folded, but they don’t fold flat like some other SUVs. To achieve a flat cargo surface, the third row seats need to be removed, and they each weigh 50 pounds.

Driving Impressions

From a stop, the electric drive can power the Yukon Hybrid up to about 30 mph for a couple of miles or so before the gas engine takes over. The transition from electric to gas power is silky smooth and once underway the ride comfort is exceptionally good for a vehicle this size. Steering feel is on the mark, and while body roll is present during an aggressive turn, it’s less than you would expect from a three-ton vehicle.

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I’m impressed with the cylinder deactivation as a tool for increasing fuel economy. With a little practice, the big V8 can be coaxed into operating on four cylinders at around 40 mph, and can do so for several miles. On the Interstate it’s not difficult to maintain four-cylinder operation at 70 mph.

The Hybrid SUV For You?

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If you are dead set on buying a full-size hybrid SUV there are only three choices, the GMC Yukon Hybrid and its corporate siblings, the Chevrolet Tahoe Hybrid and the Cadillac Escalade Hybrid. Chevy’s Tahoe Hybrid is only a few hundreds less but it’s styling is more pedestrian than the Yukon’s and the base model isn’t as well appointed. On the other end, the Escalade Hybrid is more tech heavy, more luxurious with tons of bling, however, it’s 20 grand more than the Yukon.

What the Yukon Hybrid offers is plenty of capability for work-related endeavors, hefty towing capabilities and an abundance of space and amenities for large families, even up to eight. Oh, then there’s also the 20 city/23 highway/21 combined fuel economy numbers.

What’s Next For The Yukon Hybrid?

There may not be a next GMC Yukon Hybrid. Apparently General Motors is leaning towards canceling possibly all of the hybrid variants of the new trucks and SUVs that are scheduled to debut as 2014 models at the 2013 North American International Auto Show in January or 2013 Chicago Auto Show in February. Since their introduction in 2008, two-mode hybrid SUV and truck versions have not sold well plus, it’s been reported that the 2014 hybrid development program has experienced cost overruns that has displeased management.

However, a cast-in-concrete decision has not been made and, indeed, it is possible that an all-new 2014 Yukon Hybrid could make its appearance at one of the auto shows. If so, it will continue to be built upon GM’s full-size truck platform, including a live rear axle for towing, and will not switch to a crossover design. Fuel economy gains will come from weight reduction, a smaller displacement V8 engine, upgrading the battery to a lithium-ion pack, revised electric motors and possibly, an all-new four-mode electrically variable transmission.

Prices are Manufacturer Suggested Retail Price (MSRP) at time of publication and do not include destination charges, taxes or licensing.