Lexus RX review - parsimonious SUV is still no driving machine - Engine and Gearbox
Luxury SUV is now available with a 2-litre turbocharged engine, but hybrid is still the car to go for
Other markets might be offered the RX with the 3.5-litre V6 on its own, but UK buyers can only have it in 450h hybrid guise. It’s a clever system, Lexus’ parent company Toyota having real form in hybrids - offering the RX in hybrid form over ten years ago.
Even now most manufacturers are still unable to offer a direct hybrid rival, though a few - Porsche and soon BMW - offer plug-in hybrids for greater expense. Many turbodiesels offer similar economy and emissions, though they lack the RX 450h’s party trick of being able to run on electricity alone - albeit for very short periods.
The combined power output of the V6 and its attendant electric motor, and the motor at the rear axle, is 308bhp. While that doesn't result in staggering performance it's still a reasonably pleasant engine to use, the V6 tuned for quietness and smoothness rather than maximum power. It also uses the Atkinson combution cycle to boost efficiency - in effect, those electric motors are there as much to minimise lost power from this particular combustion method as they are for boosting it over a 3.5-litre engine's normal reach.
Transmission is via an epicyclic gearbox. This mixes the varying torque outputs of the petrol engine and electric motor into one smooth shove via relatively mechanically-simple means - the CVT-style delivery may be less entertaining than using a dual-clutch transmission, but you can expect it to work trouble-free for the life of the car.
So that's the hybrid - but what about the new model? A 2-litre turbocharged four-cylinder is also available in the RX, the first time a non-hybrid model has been available in the UK since the second-generation car replaced the first RX.
It develops 235bhp at 4800-5600rpm and 258lb ft of torque from 1650rpm. It's also attached to a torque converter automatic transmission, and comes in front- and all-wheel drive forms. And that's about as much as we can say about it - it's neither as smooth nor as powerful as the V6 hybrid and suits the car's character less.