2010 Lexus RX450h

Lexus RX is the best-selling Lexus, and one in five sold is the hybrid version. It's no surprise, then, that with the new third-generation RX - the second to have a hybrid powertrain - Lexus is treading very carefully.

The design is a careful evolution, both inside and out. The car is slightly longer and wider but manages to look sleeker than before. The interior retains the traditional Lexus virtues of comfort and refinement. Lexus has joined the Germans by adopting an iDrive-style controller instead of a touch screen for its optional navigation system. But rather than a knob you twist and push, the Lexus control works more like a joystick that you move from side to side or forward and back, and then make a selection by pressing buttons on the side of the unit. It takes some getting used to.

Other new options don't require a learning curve, such as the head-up display and the curb-view camera; the latter is located in the right-side mirror, and at low speeds it shows an image of what's alongside the car. The hybrid model supplements its previous ECO indicator, which lights up when you're driving efficiently, with a selectable ECO mode, which changes the responsiveness of the throttle and instructs the climate control to use the A/C compressor more judiciously. There's also an EV mode, which extends the threshold before the engine starts, up to a still-modest 8 to 10 mph.

The changes aren't dramatic, but Lexus has given its cushy suburban hybrid a slightly greener tinge. Lexus engineers identify four elements that underpin the brand's hybrids: performance, quiet refinement, low emissions, and fuel economy. In this redesign, the latter received the most emphasis.

Whereas the standard RX350's 3.5-liter V-6 is little changed (adding 5 hp for a total of 275 hp), Lexus RX450h got a whole new gasoline engine. Replacing the old 3.3-liter is a new 3.5-liter V-6 that runs on the more efficient Atkinson cycle. EPA numbers for the front-wheel-drive RX hybrid are up by 1 mpg city and 3 mpg highway, to 28/27 mpg. The all-wheel-drive version adds 2 mpg all around and is now rated at 28/26 mpg

Despite the increased fuel economy, the RX pecking order has been preserved, with the hybrid again outmuscling the standard Lexus RX350. The hybrid's total power output is up by 27 hp, to 295 hp, and both the gasoline engine and the electric motors make more torque. Against that, however, is the car's weight gain of more than 400 pounds. Still, the RX hybrid accelerates quickly and smoothly. Once again, the all-wheel-drive model adds a third motor/generator, which is the sole source of propulsion for the rear wheels. In either version, the start-up and shutdown of the gasoline V-6 is seamless, but in steady-state cruising on level ground, there is the faintest surging as the batteries switch between charging and assisting.

© Source: automobilemag
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