The 2006 Lexus RX 400h rolling into showrooms next month isn't just America's first luxury gasoline-electric hybrid vehicle.

Filled with soft, leather-trimmed seats, standard navigation system and rear-view camera and an available high-class audio system, the RX 400h is an experiment of sorts to see how many affluent car buyers, who usually don't make fuel economy a high priority, will want a high-tech hybrid sport utility vehicle.

Some affluent buyers "want to make a statement about their social consciousness ... want to make a statement that they care (about the world and the environment), but they want to do it without compromising," said Denny Clements, the group vice president and general manager for the Lexus Division of Toyota.

With a starting manufacturers suggested retail price, including destination charge, of ,185, the RX 400h becomes the latest - and priciest - low-emission, fuel-saving hybrid on the market.

The RX 400h looks much like the RX 330 - the midsize, five-passenger SUV on which it is based. Where the RX 330 is powered solely by a 230-horsepower, 3.3-liter, double overhead cam, gasoline V-6, the RX 400h has a slightly less-powerful version of this V-6 - with 208 horsepower - mated to two motive electric motors that, all together, provide 268 horses.

One motor up front drives the front wheels; the rear motor powers the rear wheels when needed. The whole process is controlled by a computer that is part of Toyota's patented Hybrid Synergy Drive system, which is now in its fourth generation.

On paper, the RX 400h has 212 foot-pounds of torque at 4,400 rpm, but the electric motors deliver the torque from 0 rpm, so the power comes readily and eagerly in the kinds of driving situations that most drivers face every day - accelerating from a stop, merging into traffic and passing other vehicles.

In the test drive of the RX 400h, for example, my driving companion got over the speed limit smoothly, quickly and without realizing it while passing a vehicle on a country road. The 0-to-60-mph time of 7.3 seconds reported by Lexus for this hybrid is equal to that of a Mercedes-Benz ML500 SUV with a V-8 engine.

The federal government rating for the 400h is 31 mpg in city driving and 27 mpg on the highway, for a combined rating of 29 mpg.

The RX 400h puts out fewer pollutants, including 90 percent fewer smog-forming emissions, than typical new vehicles. Some of the emissions improvement stems from the fact the RX 400h can drive short distances at slow speed on electric power only, leaving the V-6 off.

The engine also can shut off on its own at stoplights, and the driver might find himself suddenly enveloped in quiet. When a driver touches the accelerator again, the V-6 might start up again to help supplement the electric power. Nothing's wrong. It's just the vehicle's way of being most efficient with its fuel, and it helps explain why the city fuel rating is higher than that for highway travel in this hybrid. On the highway, the gasoline engine has little opportunity to turn off, so there's more gasoline burned.

A driver doesn't do anything but drive the RX 400h. There's no need to plug in the electric motors. Power for them is generated on-board as the vehicle travels and is stored in a nickel metal hydride battery that fits under the rear seat cushions.

The V-6 has a confident sound when it's accelerating and isn't heard much at other times. I did hear a bit of a "whirring" at times in the RX 400h when the electric power was flowing, the radio was off, and there wasn't much other noise around the vehicle to mask the sound. Because the RX 400h can be so quiet, I noticed some wind noise around the side mirrors at highway speeds.

Handling is a bit trickier at the extremes in mountain twisties because the battery weight makes the vehicle feel as though three fat guys are sitting in the back seat, as one auto writer colorfully put it. In day-to-day travel, however, drivers are more likely to notice an occasional lightness to the steering - it's an electric power steering system for energy efficiency.

Note that the all-wheel drive is for improved on-road traction and for mild surfaces such as dirt paths. The hybrid RX is not an SUV for strenuous off-road duty. The reason? The rear electric motor will shut down before it burns itself out in rough situations such as a driver trying to climb over huge rocks or slog through mud.

Since a tachometer doesn't really provide useful information in a hybrid, where power is mixed and matched among engine and electric motor sources, this gauge is replaced by a power meter in the instrument cluster. Rear seat cushions are positioned a tad higher than in the RX 330, so the hybrid's batteries are accommodated.

There's a large display in the middle of the dashboard that can show, via an automated graphic, where the power for the RX 400h is being generated and where it's going as the vehicle travels.

The test RX 400h was so quiet at startup that I didn't always know it was on. This is because the engine doesn't need to start up right away. This hybrid can go a short distance on electric power only. Thank goodness the RX 400h instrument cluster told me the vehicle was "ready" for driving, so I didn't just sit there, wondering what to do.

The specs

VEHICLE: 2006 Lexus RX 400h, a front-engine, electric all-wheel-drive, five-passenger, midsize sport utility vehicle

BASE PRICE: ,535

DESTINATION CHARGE:

PRICE AS TESTED: ,185

ENGINE: 3.3-liter, double overhead cam, 60-degree V-6 with VVT-i mated to two motive electric motors

TRANSMISSION: Continuously variableepa

MILEAGE: 31 mpg city, 27 mpg highway

TOP SPEED: 112 mph

LENGTH: 187.2 inches

WHEELBASE: 106.9 inches

CURB Weight: 4,365 pounds

BUILT in: Japan