Introduced in 2004 as a 2005 model, the Lexus RX 400h became the first luxury crossover powered by a hybrid drive system. It was the closest thing at the time to a guilt-free SUV we’d ever seen: luxurious, powerful and more fuel-efficient than its gas-powered sibling, the RX 300.

This year, is upgrading the RX Series, including its luxe hybrid. Powered by an extensively redesigned version of the constantly evolving Lexus Hybrid Drive system, the all-new 2010 RX 450h benefits from the myriad changes and upgrades to the third-generation RX platform. It combines an impressive array of features and technologies, typical Lexus build quality and a powertrain that offers a segment-leading blend of performance and fuel economy.

Model Lineup

The RX 400h is powered by a muscular version of the gas-electric hybrid powertrain introduced in North America by the Toyota Prius in 2001. It was built around a 3.3-liter V6 gasoline engine that could develop 270 horsepower.

The new RX 450h — hybrid model designations are not tied to the gas engine’s displacement— gets a thoroughly revised hybrid powertrain and will be offered in a single trim with either front-wheel or all-wheel drive. Several packages are offered: Premium, Comfort, Luxury, Sports and Navigation, some of them interdependent, with almost 20 stand-alone optional items. Slightly larger than its predecessor, the RX 450h also offers a bit more space for five passengers.

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2010 Lexus RX 450h

A number of styling elements distinguish the RX 450h from its RX 350 sibling, most notably the design of its grille and front bumper. It also gets a set of exclusive alloy wheels with thinner, split spokes, and blue accents have been added to the headlights, rear lights, hybrid-specific badges and gauge cluster. Finally, the Aurora White Pearl color is another RX 450h exclusive, as well as a black and light gray interior trim package with black accents.

Optional and exclusive on the RX 450h are LED headlamps, complete with headlamp washers that will set it further apart from the RX 350. These will also last longer and draw less power over their useful life.

Under the Hood

Pop the hood and you’ll find an all-new version the high-tech Lexus Hybrid Drive system. It combines a new 3.5-liter V6 engine running on the Atkinson cycle, lighter and more powerful electric motors, and a smaller, lighter and more potent control unit. Under the Atkinson cycle, intake valves close later to delay compression and reduce energy loss. This improves combustion and fuel economy while reducing exhaust temperature. A new system called the Exhaust Gas Recirculation (EGR) system reduces energy loss further, to improve economy by eliminating the fuel enrichment needed to avoid overheating catalytic converters under high loads.

Another new system recovers heat from the exhaust pipe to accelerate engine warm-up and allow the crucial engine-stop function to kick in much earlier, more often and for longer periods, improving fuel economy and reducing emissions appreciably. With its selectable EV mode, the RX 450h can also run short distances on electric power, but only under specific conditions.

Discuss: 
Does a hybrid-powered luxury crossover like the RX 450h offer the best of both worlds?

The V6 engine by itself delivers 245 horsepower at 6000 rpm, up 37 from the RX 400h’s 3.3-liter V6. Torque is rated at 234 lb-ft at 4800 rpm, up from 212 at 4400 rpm in the previous model. The system’s combined maximum output is 295 horsepower, which is a 27-pony increase over the RX 400h. Yet the RX 450h’s Environmental Protection Agency fuel-efficiency ratings of 28 mpg city and 27 mph highway (26 mpg for the AWD version) are 8 to 12 percent better than its predecessor. The RX 450h is certified as a Super Ultra Low Emission Vehicle (SULEV) in California, which means that it produces almost 70 percent less emissions than other vehicles.

The new hybrid system’s 288-volt nickel-metal hydride (Ni-MH) battery pack, nestled under the rear seat, is smaller and lighter than in the first-generation hybrid RX. The front-wheel-drive RX 450h’s hybrid powertrain uses two electric motor-generators, and the all-wheel-drive RX 450h gets a third one to drive the rear wheels without a transfer case or driveshaft. The power-steering pump, water pump and air-conditioning compressor are all driven by electricity instead of the engine, which reduces parasitic losses, as well.