More than once, while negotiating bumper-to-bumper traffic on a recent three-hour nightmare drive to L.A. from my Orange County, Calif., home, I thought it strange that it took until the 2008 model year for car companies to introduce a full-size hybrid SUV.

I mean, SUVs just seem destined for fuel-efficient hybrid engines, right?

So, I drove to Santa Monica's oceanview Fairmont Miramar Hotel for a first look at GM's 2008 two-mode hybrid GMC Yukon and Chevrolet Tahoe.

What did I find? GM has really delivered one hell of an SUV. I discovered that GMC's 6-liter V8 hybrid Tahoe and Yukon are perhaps the most smooth-riding and least noisy hybrid models (car or truck) on the market today.

Although the gas mileage statistics for these models are not yet formally government rated, GM says its Tahoe and Yukon hybrids may get up to a 40 percent improvement in city fuel economy over their non-hybrid versions and possibly a 25 percent improvement overall. (The same engine will also be available on the 2008 Cadillac Escalade, GMC Sierra and Chevy Silverado.)

To hear GM's head engineers talk about this engine is like listening to a pilot talk about flying a plane. It's complicated.

Basically, there are three engines, one gas and two electric ... motors to be exact (one of which is located under the second row seats). All of the engines are highly interconnected machines, giving the Tahoe or Yukon (and the upcoming 2008 Escalade, Sierra and Silverado) a hefty 332 hp.

"This is a no-excuses hybrid," said GM's chief hybrid engineer Mark Cieslak. "We took a full-size truck to the next level by improving fuel efficiency and performance."

Sure, GM did bring better fuel efficiency to these utilitarian vehicles with seats enough for eight passengers and a 6,000-lb. towing capacity, but did their engineers really improve performance?

"GM looked at every single aspect of these SUVs, from the engines to the interiors and exteriors, to extract as much energy savings as possible, Cieslak said." For example, the electric variable transmission (EVT) was designed to take full advantage of the engine to maximize fuel efficiency. In conjunction with the EVT, GM is using Active Fuel Management , which shuts down four of the eight cylinders in the engine when needed, further increasing fuel efficiency. And, these full-size SUVs run on electric power alone up to 32 mph. To capture even more available energy, GM's engineers developed a "fully-blended regenerative brake system" that gathers energy every time you use the brakes and uses it to recharge the battery pack.

Aerodynamics were also a big consideration, Cieslak said, who also states that even the wheel spokes were redesigned by world-class aerodynamics specialists. In addition, GM took "mass reductions" in the SUVs' weight by creating an all-new aluminum body and "thin profile" seats, he said.

But Cieslak was most excited about the engine's "brain," explaining that the engine's computer sizes up the driving situation every 100 milliseconds, instantly making decisions on behalf of the driver, ultimately deciding the best possible energy solution for even greater performance and fuel efficiency.

That all sounds rather fantastic, but how do these new hybrid trucks really drive? When I got behind the wheel that day in Santa Monica, I honestly was rather skeptical, because I've driven every hybrid model on the market today and I'm usually somewhat disappointed in all two-mode hybrids for their lack of acceleration and uncommon gurgling engine noise.

However, after driving on a sunny California day through Santa Monica's rolling hills and city traffic, I came away completely impressed. Not only do these new hybrid SUVs power over hills and handle perfectly, but they are the most non-hybrid-sounding vehicles available on the road. In fact, I wouldn't have known these trucks were hybrids by either engine noise or handling.

Regarding pricing, the GM reps were rather vague, although they did say the cost of these hybrid versions would be somewhere around the 2007 Chevy Tahoe LT and GMC Yukon XL, both of which have an MSRP starting at $39,000. Thus GM is pricing these models without a "hybrid premium" as have other hybrid makers.

So when will these technology-laden hybrids be on the dealership floors? GM officials say they are hoping to sell some of the "world's first full-size hybrid SUVs" as Christmas presents, but if not, certainly after the first of the year.

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