In addition to the new Lexus HS 250, Lexus has an entire line of hybrids that are almost indiscernible from a distance from their gasoline-only counterparts. Of those, the bestseller is by far the RX 450h, which brings a hybrid halo to this very popular luxury crossover.
We've had a number of engineers tell us that the best pairing for a hybrid vehicle includes a small, efficient gasoline engine that's relatively torque-weak, combined with a relatively strong electric-drive system. That way, the electric motors supply the torque needed for responsiveness and grunt off the line at traffic lights, while the gasoline engine does its part for passing and expressway cruising.
That's not the case for the 2010 Lexus RX 450h, which has, as part of its system, a 275-horsepower, 3.5-liter Atkinson-cycle V-6 that's actually very torquey on its own. It's quite possible Lexus could have achieved better mileage this time around with a four-cylinder as part of the system.
The simple answer, we suspect, is that it's all in the name of refinement. While the new 2010 Lexus HS 250h gets loud and boomy when you accelerate moderately or rapidly, as we reported in a follow-up drive last week, the RX 450h feels all the part of a Lexus. Drive it gently and you'll glide from stops in electric-only mode, with the V-6 almost imperceptibly kicking on at 20 or 25 mph, typically. Drive it a little more rapidly, to go with the flow of traffic, and the V-6 thrums in the background, with the continuously variable transmission generally keeping the revs well below 2500 rpm unless you're close to full throttle.
Even then, a stomp to the floor doesn't betray that Lexus smoothness, though it's accompanied by a bit of a high-pitched whine. Altogether the system makes 295 hp, with lots of available torque, so the powertrain feels relaxed and up to the task in everyday driving—and again, almost indiscernible from a non-hybrid crossover.