Gas/electric hybrids are becoming commonplace in economical cars, trucks, and SUVs. But does the formula work in a luxury sport/utility? Lexus is banking on it, and after driving the RX 400h for two days, we think the automaker is on to something.

Based on the RX 330, the hybrid retains the 208-horsepower, 3.3-liter V-6, adding a 167-horsepower/247-pound-foot permanent magnet electric motor up front and a 68-horsepower electric motor for the rear wheels. While the rear electric motor generates 96 pound-feet of torque, a 6x gear reduction boosts rear-wheel torque to an impressive 650 pound-feet. A third electric motor (at the bellhousing) functions as a generator, engine starter, and ratio control for the continuously variable transmission and can charge the 288-volt battery pack.

Slip the key into the 400h's ignition, give it a twist, and it's...quiet. The gas-burner doesn't turn over, yet, put the hybrid into gear, depress the accelerator, and the front electric motor pulls you away.

Adding pressure to the accelerator, the V-6 eases to life and the CVT seamlessly flows through the ratios. Putting the go-pedal to the floor places the 400h into hybrid hyperdrive, as the battery packs send a full load of juice to both electric motors, planting your back firmly into the seat. Let off the gas, and the electric motors go into regenerative braking mode to keep the batteries topped off.

Even with power that mimics a small-block V-8, the 400h delivers impressive fuel economy. Preliminary EPA estimates are 30 (highway) and 28 (city). On a 412-mile loop that included city, mountain, and highway roads, our light-footed drive averaged 34.4 mpg, according to the pre-production Lexus' trip computer.

Our only real disappointment with the 400h is its off-road ability. True, it'll handle snow and graded dirt roads, but Lexus officials don't recommend taking the hybrid off the beaten path; the aft electric motor is air cooled, and there's a concern for excessive heat buildup. However, towing is fine, as long as you're pulling 3500 pounds or less.

For the majority of SUV owners who will never see anything worse than inclement weather, the RX 400h provides luxury-SUV appointments with a powerful and economic platform.