2008 Chevrolet Tahoe Sport Utility

Here's what you know: Hybrid vehicles are happenin'. Here's what you may not know: All hybrids are different. And in that murky space between what you know and what you don't there lies the potential for mayhem.

Lately, for example, much has been made about a 38-percent gain in sales of hybrid vehicles. As if to pepper the pot, it's also pointed out that overall vehicle sales are down about three percent. Ergo: Hybrids are the bomb!

If only. Hybrids account for only two percent of vehicles on the road in the U.S. (up from 1.45 percent for those of you checking the math). Speaking in round numbers, that means the number of hybrids on the road totals approximately 300,000-about 6,000 per state. Yet the three-percent decline in overall auto sales translates into 450,000 vehicles. The increase in hybrid sales can't even keep pace with the decline in sales of every other type of vehicle. Clearly, the hybrid revolution has quite a way to go yet.

Still, there is indeed much ferment in the "alternative powertrain" segment of the auto market, of which hybrids are just one example. And although it's a transitional technology at best, a petro-electric hybrid integrates several ingenious systems by means of truly phenomenal data processing. A well-designed hybrid is a delight to drive; and before long, lo and behold, a hybrid driver becomes a junior physicist seeking to optimize the equilbrium between fuel consumption and regenerative power production. The trip is suddenly more fascinating than the destination. And if even a little of the scientific sophistication of a hybrid powertrain were to rub off onto our nation of accelerator-jockeys, so much the better for us all.

Chevy's hybrid-version of its iconic Tahoe is remarkable on many levels. To the militant fringe out there, the very idea of a "responsible" SUV merits a gasp (as if hybrid-powered trains and busses were steps in the wrong direction themselves). Technologically, grafting a petro-electric powertrain onto a vehicle weighing nearly three tons, towing 6,000 pounds more and seating eight adults is a tour-de-force of applied physics. The fact that it took a consortium of GM, Mercedes-Benz and BMW to do so only underscores that point.

At the heart of the Tahoe system is a 6.0-liter pushrod V8 rated 332 hp and 367 foot-pounds of torque. Two 60-kw electric motors provide 120kw of propulsive thrust capable of moving the Tahoe by electric power alone in many circumstances. Ingenious robotics-like systems transform the V8 into a V4 when extra engine displacement isn't required, and toggle the four-speed automatic transmission into a continuously variable one when maximum fuel efficiency is required.

The Tahoe Hybrid is a complex, highly redundant, computer-dependent integrated system. But here's the key: No one has to notice. Based on one of the nicest, plushest, stateliest SUVs on the market, the Tahoe Hybrid manages to cogitate its brains out without driver or passengers being any the wiser. In four-wheel-drive configuration, moreover, the Tahoe Hybrid achieves 20 mpg/city, 20 mpg highway. That "city" figure represents an improvement of more than 45 percent, by the way.

At $52,395, this hybrid SUV isn't cheap; but it is dolled up with almost every the top-of-the-line feature Chevy has to offer, like DVD and OnStar navigation systems, XM Satellite radio, dual-mode climate control, back-up camera and so-forth. The NiMH battery pack takes up room, so maximum cargo space, after the third-row bench is removed and the second row folded, is only 109 cubic feet. But if hauling, towing and car-pooling are unavoidable elements of your lifestyle, Chevy's Tahoe Hybrid makes an elegant argument in favor of science-flavored efficiency.

For Chevrolet to commit to hybrids to the extent it has in 2008 is to bestow an endorsement of seismic proportions. Because the three Chevy hybrids-a sedan, an SUV and a full-size pickup-aren't wonky-looking car-bots fresh from the science-fair. They're practically sized, hard-working, traditional-looking vehicles that won't scare anybody. And that is the best favor Chevy can do-has done-by adopting hybridology. There's nothing threatening about it.

As already pointed out, however, no two hybrid schemes are alike, and the new Malibu and Tahoe hybrids are a case in point. In the Malibu, the electrical side of the petro-electric equation plays a subordinate role. Yes, there's a nickel-metal hydride (NiMH) rechargeable battery pack, but it powers an auxiliary motor rated at only 4 kilowatts of torque assistance. In other words, the Malibu's four-cylinder "Ecotec" gasoline engine is the workhorse, and the electric motor pipes up only for very-low-speed chores, auto-restarts after the engine shuts down during idle and the operation of cabin conveniences like air-conditioning.

Still, because Malibu's is a relatively simple, no-frills hybrid system, its price tags is similarly unfrilly and affordable. It is, in fact, among the least expensive hybrids on the road at $22,140; and its mileage ratings of 24 mpg/city, 32 mpg/highway are quite attractive for a five-seater sedan.

What's more persuasive yet is the Malibu's 2007 makeover that resulted in an American-made sedan (albeit with a significant help from GM's Opel Division in Germany) that is roomy, responsive and attractive. For $2,500 less than the Malibu Hybrid, in other words, there's a base-model Malibu LS that still ekes out 22/30 mpg with similar horsepower and torque.

Chevrolet trims out its Malibu Hybrid with a few more upscale features, as if to compensate for mediocre acceleration and a rather lifeless four-speed automatic transmission. But because this petro-electric version of the Malibu introduces hybridology in a non-threatening and relatively inexpensive fashion, it's more likely than most rivals to win skeptics over to the "alternative powertrain" cause.

Sport/Utility Vehicle; 4-door, 8-pass.; 6.0-liter OHV V8 w/ vvt & 120kw NiMH electric motor-generator; 4WD, 4-sp. "two-mode" auto; 332 hp/367 ft.-lbs.; 20 mpg/city, 20 mpg/hwy w/ regular; cargo: 17-60-109 cu. ft.; tow: 6,000 lbs.; as-tested price, w/ front ind. suspension & 4-wheel ABS disc brakes, AM/FM/CD/XM audio, OnStar, dual-zone climate control, DVD SatNav, 18-in. wheels, front/front-side/head airbags: $52,395

Sedan; 4-door, 5-pass.; 2.4-liter DOHC "Hybrid Ecotec" inline-4 w/ 4kw NiMH electric motor-generator; FWD, 4-sp. auto; 164 hp/159 ft.-lbs.; 24 mpg/city, 32 mpg/hwy w/ regular; trunk: 15 cu. ft.; as-tested price, w/ 4-wheel ind. suspension & ABS disc brakes, stability control, AM/FM/CD/XM audio, OnStar, "Eco" HVAC, 16-in. wheels, front/front-side/head airbags: $22,790.