The driving force behind the Lexus RX 400h is Toyota's Hybrid Synergy Drive technology, which lets the car run on either gas, electric, or both power sources. Power surges from a 208-horsepower 3.3-liter V-6 gasoline engine, and since this is an all-wheel-drive vehicle, the engine gets help from not one but two electric motors (front and rear). Together, both power trains pump out an exhilarating 268 horsepower.
Like other hybrids on the road today, the RX 400h uses the electric motors to get moving and at low speeds, but once you feel the need for speed, the car taps into the gas engine for a boost. The Lexus engineers show their pride in the electrical half of the power train by including three ways to watch all the action. A large gauge on the left side of the instrument panel shows how hard the electric motors are either working or charging. For a more detailed view, you can switch to the main LCD in the center console, which displays how gas and electric power are distributed in your vehicle. Or view a smaller version of this screen embedded in the speedometer display, which you can call up with a few taps of the Display button on the steering wheel.
As with other hybrids, nothing happens when you twist the ignition key. The car wakes up electronically, ready to move under electric power alone until you pass the 25mph mark, at which point the gas engine kicks in. There is an amusing yet serious sidebar to this arrangement; parking valets, friends, and car wash attendants who get in your RX 400h may sit there madly twisting the key, wondering why it won't start. Less entertaining is the way you may startle pedestrians by creeping up behind them, running silently on electric power, especially in noisy parking garages. It demands the driver be aware of the unique sound print of this vehicle.
Once underway, you'll quickly appreciate this vehicle's main selling point: it's fast. When the electric motors kick in, power delivery comes on as if from a turbocharger, roundly but forcefully. The numbers tell it all. The RX 400h goes from 0 to 60mph in 7.3 seconds, a hair slower than the Honda Accord Hybrid but faster than the Ford Escape Hybrid.
The power steering on the RX 400h sometimes feels a bit rough, an issue we've noticed on other hybrids. Conventional cars obtain constant hydraulic pressure for the power steering system by running a pump off the crankshaft pulley. Because the gas engine on the RX 400h isn't always on, its power steering runs off a 42-volt electric motor that is always operational, preventing interruptions in power assist. The downside we noticed was a decidedly notched feel to the steering at times, almost as if the initiation of assist could use a little more damping. It's not a big issue, but in a vehicle of this caliber, we notice it more than we would in, say, the Toyota Prius.
If you like Lexus RX styling historically, you'll appreciate the RX 400h. It carries over most of the design cues that have always identified the RX series, with the notable deletion of the separate rear-quarter windows of first-generation vehicles. Those windows have now been absorbed ahead of the C-pillars as glass sail panels, giving the side view of the RX a sportier look more reminiscent of a fastback. Cabin room is good, which isn't hard to do in an SUV. We felt visibility was a little sketchy around the rear-quarter blind spots, thanks to those new, more massive C-pillars.
As we would expect in a luxury vehicle, the Lexus RX 400h came with a nice set of digital comforts as part of the standard package: a voice-activated DVD navigation system, a backup camera, and Bluetooth technology for hands-free cell phone use. The seven-inch, touch-screen LCD mounted high in the dash caught our eye, thanks to the lack of distractions around it. We liked that Lexus opted not to go with the multifunction control knob that's becoming increasingly common in cars of this class; in fact, most controls in this cabin looked instantly familiar. The only ones that take some familiarization are the black push buttons along the bottom edge of the LCD for operating the display's functions.
The main reason for the screen, of course, is the Lexus voice-activated DVD navigation system. Like the navigation system found on the Lexus GS 430, we found its map display to be disconcertingly grainy. While taking nothing away from its functionality, it imparts a feeling of crudeness that isn't satisfying--or easy to overlook--in a $52,000 car. That aside, the navigation system performed well, providing us with voice-guided directions and quickly recalculating our route as we intentionally made wrong turns. With the touch-screen interface and the onscreen keyboard, entering a destination is fairly painless, although the car must be at a stop. The system recognizes some voice commands, but you can't enter destinations via this method.