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Road Test: 2010 Lexus RX 450h, the hybrid that's similar...but different

The 2010 Lexus RX 450h is just like the 2010 Lexus RX 350, at least except where it isn’t, and the differences are not very big…or yes it is.

 

Let’s get past the basics. Lexus RX models are mid-size crossover-styled SUVs. the RX 350 having a conventional drivetrain with a 3.5-liter V-6 engine and front or all-wheel drive, as we described in a recent road test.

 

The 2010 Lexus RX 450h, however, is a full hybrid similar to (yet again different from) the Toyota hybrid drive system. The RX 450h updates last year’s RX 400h with a new engine and a variously enhanced drivetrain. It’s still capable, as are all Toyota/Lexus hybrids, of operating under electric-only, gasoline-engine-only or combined modes.

 

Engine  The new engine is a 3.5-liter Atkinson-cycle V-6. An Atkinson-cycle engine is a conventional four-stroke gasoline engine except for valve timing. The intake valves close later than a conventional engine and without going into technical details, it reduces energy losses in the engine for more efficient combustion and better fuel mileage. The RX 450h’s engine is rated at 245 horsepower, up from 208 in the previous RX 400h.

 

The RX 450h stores its 288-volt nickel metal hydride (Ni-MH) battery pack under the rear seat. It’s more compact and lighter than that of its predecessors. The power control unit that houses the power converter, inverter and condenser—we’ll just have to learn this new electrical jargon in this new era of hybrids and electric cars—is also smaller and lighter.

 

AWD or FWD  Like the RX 350, the RX 450h is available in front or all-wheel drive versions. A bit of gearhead info (the rest of you can step out for coffee): The front-drive version has two motors. The first is called MG—for motor-generator one—which is the starter for the gas engine and it’s an engine-driven generator that can charge the battery pack or power other electric motors (power-steering pump, water pump and air-conditioning compressor drive motors) as needed. The electric motor that actually drives the front wheels is MG2 and the power from it and the V-6 engine goes to the drive wheels via a planetary gear-type continuously variable transmission. MG1 controls the output speed of the transaxles through the planetary gear set, without clutches or viscous coupling.

 

(OK, everyone back in): This new arrangement of hybrid components allows greater range of performance from the electric motor and that, along with a more powerful gas engine, makes a stronger performer overall. Driving the RX 450h in coastal Georgia we didn’t have any hillclimbing opportunities but full throttle put paid to the reputation of hybrids being poor performers.

The 2010 Lexus RX 450h is also available with all-wheel drive and rather than a driveshaft-type arrangement of a conventional all-wheel drive system, the RX 450h just throws on another engine out back (MGR), like the 2009 Toyota Highlander Hybrid we tested. The hybrid system varies front and rear torque distribution electronically, depending on traction availability.

 

All three of the RX 450h’s motors can function as generators for recovering energy, of course. There’s a setting to that allow the driver to use engine braking and a new “AI-SHIFT” that keeps the transmission in the best range for driving downhill.

 

Modes, we got modes  The driver of an RX 450h also has three special driving modes in addition to the default “normal” setting. A new “ECO mode” softens the response of the throttle to reduce the aggressive acceleration—and electronic nanny—and it also reduces running the air conditioner compressor during acceleration even more than usual. Both help give better fuel economy.

 

An “EV drive mode” allows operation on just the electric motors for operation in quiet areas, such as hospital corridors, or to reduce emissions in enclosed area such as parking garages. We think it also would be useful for creeping up on and scaring people in supermarket parking lots and sneaking home late at night. But that’s your call.

 

 

The Lexus RX 450h transmission also ahs a sequential shift mode that allows the CVT to imitate a six-speed manually-shifted transmission.

 

A worthwhile feature on the RX 450h is an exhaust heat recovery system. When the engine coolant temperature is low, it “captures” waste heat by routing the exhaust through a trap that pipes the heat back to warm the coolant. This helps the engine warm more quickly, helping the catalytic converters get up to temperature sooner for reduced emissions and also improving fuel economy. By keeping the engine warmer, it also means the engine has to run less just to maintain cabin temperature when it’s cold, as we noticed in our test of the 2009 Toyota Camry hybrid.

 

The chassis and other features and options are similar though not identical to those of the Lexus RX 350 recently reviewed. Most notably, the Remote Touch navigation controller is in both cars. The RX 450h, on the other hand, has electronically controlled brakes calibrated to work with the Vehicle Dynamics Integrated Management (VDIM) handling technology standard on the hybrid (and optional on the RX 350).

 

Cosmetics  Cosmetically the RX 450h has distinctive optional 19-inch wheels and the Lexus badges on the grille and liftgate have a “Lexus hybrid blue” background rather than black. The front bumper and grille are different and the RX 450h has optional LED headlights with longer life and lower energy consumption.

 

Our driving was all daylight so we didn’t get to test even the standard adaptive lighting that anticipates where the RX 450h will be in three seconds and points both high and low beams there (other systems steer only low beams).

 

However on two passes around a 20 mile test loop we recorded 35 mpg when driving to maximize gas mileage but only 28.5 mpg while driving “normally,” i.e., without balloon-footing or watching the various fuel consumption gauges. Either way it’s phenomenal for this size of vehicle.

 

We did notice that the engine seems to be required for most normal driving operations, more so than the Two Mode Hybrid General Motors products we’ve driven the 2008 Chevrolet Tahoe Two Mode Hybrid, The Cadillac Escalade Hybrid and the Saturn Vue Two Mode Hybrid. While those vehicles could easily maintain fifteen miles per hour on the electric motor alone, the Lexus RX 450h seemed all too eager to turn on the engine.

 

Indeed, the engine can easily be felt starting up when pulling away from a stop sign, for example. At full throttle, the continuously variable transmission effect—the engine pitch staying almost steady as the vehicle gathers speed—is evident. Otherwise the powertrain is simply unobtrusive.

 

That unobtrusiveness is the similarity between is how the 2010 Lexus RX 350 and Lexus RX 450h. Both are mostly seam-free in operation and comfortable as fuzzy slippers.

 

 Pricing for the RX 450h hasn’t yet been announced. The RX 350 is on sale now, the RX 450h not available for several months. Expect the 2010 Lexus RX 450h to sell for about $7,000 more than its two and four-wheel gas engined equivalents, or about $44,000 and $47,000 respectively.

 

What price hybrid?  From a strict dollars-and-cents perspective, the RX 450h won’t—barring any massive price spice at the gas pump lusted after by some 40 mpg-ers—pay back the extra purchase cost of the vehicle in fuel savings. On the other hand, if sending money to Tokyo rather than oil sheiks and anti-American South American dictators gives the RX 450h owners the warm fuzzies (see slippers above) and owners prefer to get their fuel savings in a well turned out luxury crossover SUV, then the differences between the two versions of Lexus’ RX models will make the RX 450h owner very happy indeed.