The 2009 GMC Yukon Hybrid has a towing capacity of 6,200 pounds. As for gas mileage, expect between 21 mpg and 22 mpg.

GM

After years of imbibing on mammoth SUVs, buyers are shunning these big boys for smaller alternatives.

Yet some folks need the space and towing capacity that full-size SUVs provide. What to do if you have a green conscience? Try the vehicle I’m driving.

Cruising silently as it runs solely on electricity, the 2009 GMC Yukon Hybrid is a perfect solution. As I jump on the interstate, the gas engine springs to life.

The fuel consumption on my test drive, 21.5 mpg, is respectable for a 2½-ton truck that can tow 6,200 pounds.

The rear-wheel-drive Yukon Hybrid is EPA-rated at 21 mpg in the city and 22 mpg on the highway. All-wheel-drive models earn 20 mpg for both ratings.

That may not sound like much, but the EPA says opting for the Hybrid over a standard gas model saves as much as $854 a year in fuel costs.

Still not impressed? Consider the Hybrid’s fuel economy is equal to that of many midsize sedans, none of which has this truck’s capabilities.

Credit goes to GM’s new dual-mode hybrid system.

Like the hybrid systems from Toyota and Ford, the GM system runs solely on electric power at speeds up to about 25 mph. That’s when the gasoline-fueled 6-liter V8 kicks in.

Once the vehicle gets to highway speed, however, the GM system adds electric power to reduce the vehicle’s dependence on the gas engine. That’s where it differs from its competitors — thus the “dual-mode” moniker.

And when the gasoline engine is in use, it’s not always employing all cylinders. Gently cruising down the street or cruise-controlling at highway speed? The engine uses only four cylinders. Need to pass a slow-moving car? The other four cylinders come on line instantly. The operation acts seamlessly. Only the dashboard-mounted gauge reveals the truth.

The battery pack that powers the electric motors never has to be plugged in; it’s recharged by the gas engine. The Yukon’s brakes also recharge the battery pack by capturing energy during deceleration and funneling it to the batteries.

Like all hybrids, the engine shuts off when the vehicle comes to a stop, restarting upon acceleration.

Otherwise, the Yukon’s functionally makes it hard to tell this is a hybrid. There’s ample power available for hauling people or cargo, and the driveline is available with either rear-wheel or all-wheel drive.

This is a truck, so there’s body lean in corners and some softness in the suspension to smooth out the ride over neglected highways. The Hybrid’s not as refined as a crossover, but this is no rough rider by any means.

Four-wheel antilock disc brakes, stability control, traction control, rear parking assist, remote keyless entry and remote vehicle start are standard.

Inside, the instrument panel is easy to use and clearly marked. The front seats are large and comfortable, although there’s little side bolstering. The rear seat is comfortable for three adults.

Opting for the Hybrid means doing without a spare tire, but GMC provides an inflator kit with tire sealant in its place. There’s also no third-row seating as it’s been axed to make room for the battery pack and transmission.

Another gripe: The vehicle has way too many hybrid badges on it. It’s absolute overload.

While it shares its design with the Chevrolet Tahoe, the GMC has a more machined, tougher look. The GMC Yukon Hybrid costs thousands more than the standard version and $465 more than the Chevrolet Tahoe Hybrid, and to some, its fuel-economy advantage won’t offset its added price.

But for those who need an SUV and want to conserve as much fuel as possible, the GMC Yukon will prove a pragmatic choice.2009 GMC Yukon Hybrid

What we say: Heavy duty gas-sipping SUV

Pro: Almost 22 mpg

Con: Added cost may put some off

STATS

Engine: 6-liter OHV V8

Wheelbase: 116 inches

Length: 202 inches

Weight: 5,617 pounds

Cargo space: 60.3 cubic feet

Towing capacity: 6,200 pounds

EPA rating (city/highway): 21/22 mpg

Fuel economy: 21.5 mpg

Fuel type: Regular unleaded

Base price: $50,920

As tested: $54,160