The 2009 Lexus RX is offered in two primary models: the RX 350, which is powered by a 270-horsepower, 3.5L V6, and the RX 400h, which has an advanced hybrid system combining a 3.3L V6 and an electric motor system, making a combined total of 268 horsepower. The 400h's Lexus Hybrid Drive is a "full hybrid" system, meaning it can operate on electric power in some low-speed stop-and-go conditions, greatly increasing fuel efficiency. Utilizing battery packs located underneath the rear seats, the system recovers some energy during braking and coasting. Electric motors assist the gasoline engine with extra power for accelerating and passing. Both RX models are offered in either front-wheel-drive or all-wheel-drive versions. In the RX 350, the available full-time all-wheel drive system has a viscous limited-slip center differential and distributes power to the front and rear wheels with a 50/50-split in normal driving, sending more to the wheels with more traction when needed. In the 400h, an electric motor drives the rear wheels independently. According to Lexus, both the front-wheel-drive version of the RX 350 and the RX 400h can accelerate to 60 mph in 7.3 seconds. The 400h, however, has superior fuel economy ratings of 27 mpg city, 24 mpg highway. Extra attention has been paid to noise and vibration in the RX. Vibration-canceling engine mounts, an acoustic windshield, and extra sound insulation are used. There's also an available air suspension system, which has four ride-height settings. A "high" mode is designed for rough surfaces at speeds slower than 30 mph. "Low" mode lowers ride height by 0.6 inches for improved handling, and an even lower "access" mode for easier entry, exit, and loading. All RX models have five-passenger seating, with a 40/20/40 split folding rear seatback that both slides and reclines. With the seats folded down, the 28.3-cubic-foot cargo capacity can be expanded to nearly 85 cubic feet. All RX models have extensive safety features, including vehicle stability control (VSC), anti-lock brakes with brake assist, side curtain air bags, front-seat-mounted side air bags, and a driver's knee air bag. On 400h models, there's also the Vehicle Dynamics Integrated Management (VDIM) system, which seamlessly integrates many of the vehicles systems, including the ABS, VSC, traction control, and steering assist, to enable it to more quickly anticipate the loss of control and make corrections. Both the RX 350 and RX 400h are available very well equipped, and include a power liftgate, dual-zone automatic climate control, ten-way-adjustable power front seats, real wood interior trim, and heated auto-dimming exterior mirrors.