Perennial Golden Child of the Lexus lineup, the segment-leading RX series has undergone a full makeover for 2010. Growing marginally in size but materially in style, refinement and creature comforts, the gasoline-powered RX 350 is already doing its part to win over new fans in the crossover market. It will soon be joined by a hybrid stablemate, the new RX 450h. We recently spent time in an all-wheel drive version of this more eco-friendly upgrade to see how well it made the generational transition.

Successor to the original RX 400h that appeared in 2005, the new 450h is fitted with the latest-generation Lexus Hybrid Drive System, which is basically a variation on Toyota's Hybrid Synergy Drive. While both the RX 350 and RX 450h have a 3.5-liter V6 underhood, the hybrid's modified version employs a Lexus-first use of Atkinson Cycle delayed intake-valve timing and introduces a new exhaust-heat recovery system as well as a slick cooled exhaust gas recirculation setup, all of which help enhance its mileage-making skills.

On the electric side of the equation, the 2010 hardware upgrade teams this more efficient six with a scaled-down but more powerful nickel-metal hydride (Ni-MH) battery pack that powers smaller, lighter electric motor/generator units -- two in the front-drive 450h, three in our all-wheel drive tester -- via a downsized but more efficient controller. The combined system output is a stout 295 horsepower, up 27 ponies from the 400h package. Backed by a continuously variable automatic transmission (CVT) that features a "Sport" mode with six "virtual" ratios, this gas/electric package nets the front-drive 450h EPA numbers of 32/28/30 mpg city/highway/combined and earns the all-wheel-drive model 30/28/29 mpg marks. In just over 300 miles of mixed-mode motoring, our vehicle tallied up 27.1 mpg; admittedly below its bogey but still quite respectable for a 4,652-pound vehicle that can sprint to 60 mph in less than eight seconds and tow 3,500 pounds. And while the start/stop recycling "bumps" were hardly intrusive in the past, they're now virtually imperceptible.

Green aspects aside, the new 450h is designed to expand on the RX's well-established reputation for being easy to drive and even easier to live with. Beyond a few unique trim treatments that set it apart from the RX 350, the two reinforce most of their otherwise-shared "L-finesse" exterior design character with an equally new wood-and-leather accented interior treatment that offers more spacious adult-scaled seating -- in both its well-formed 10-way power front buckets and the 40/20/40 sliding/reclining split rear bench. When hauling takes priority, a simple seatback flipdown expands cargo capacity from 40.0 cubic feet to 80.3. Although exterior size and wheelbase grew little, the RX's front/rear track dimensions both widened to improve stability while a retuned and redesigned suspension delivers crisper handling and bettering ride compliance in any configuration.

As before, the new RX brings a bounty of comfort/convenience/safety features which are augmented in the 450h by upgrades like leather upholstery, an electric air-conditioning compressor, the VDIM (Vehicle Dynamic Integrated Management) system and its own dedicated hybrid-centric display readouts. It also introduces several new techno touches for 2010, including the first use of a white OLED (Organic Light Emitting Diode) instrument display and Remote Touch, a force-feedback-equipped multi-function controller that sits in the center console on all RXs equipped with the optional Naviation system. Replacing the old Touch Screen Interface, Remote Touch acts like an inverted computer mouse and brings point-and-click convenience to setting and engaging navi/audio/climate functions while decreasing the button/switch count.

Despite numerous package upgrades, the $44,125 base price on the new RX 450h is actually $230 less than the 2009 400h. However, loaded with extras that include everything from the aforementioned Navigation System -- with or without Dual-Screen Rear-Seat DVD Entertainment -- and Mark Levinson Surround Sound Audio to Bi-Xenon Adaptive Front Headlamps, Intuitive Parking Assist and the Pre-Collision System with Dynamic Radar Cruise Control it can easily top the $50K mark. Regardless of how its appointed, Lexus anticipates this latest incarnation of RX hybrid will continue to account for nearly 20 percent of the total line mix, which is currently projected to hit about 80,000 units.

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