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.
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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.