Category: Sporting 4x4s 
Price Range: No data available
Clever fuel-saving technology, "green" image, Lexus reliability and quality, refinement and high equipment levels, value for money, smooth and quiet ride.
Not quite as planet-saving as the hype suggests, not particularly roomy, vague electric steering and drive-by-wire controls, shallow boot, not as dynamic to drive as many rivals. It's also neither a proper off-roader nor a strong towing vehicle.
A step in the right direction when it comes to reducing fuel consumption and emissions from large SUVs, if not a revolution in environmentally-friendly motoring. A thoroughly pleasant vehicle to spend time in, but it's rather a case of style over substance as it's not a particularly versatile 4x4.
Lexus hasn't come up with a diesel-powered RX yet, but this petrol-electric hybrid - developed specifically for the diesel-averse Americans - offers some useful fuel savings. In a nutshell, it combines a 3.3-litre V6 petrol engine (208 bhp) and two electric motors, one driving the front wheels and the other the rear, to give a total power output equivalent to 269 bhp. This is a powertrain along the lines of that in the Prius hatchback, with the additional motor driving the rear axle giving four-wheel drive when a loss of grip is detected; as in the Prius, the engine and motors are combined with a stepless, seamlessly-changing CVT (continuously-variable transmission) gearbox.
The RX 400h (the '400' hints that its performance is equivalent to that of a conventional 4.0-litre engine, and the 'h' stands for hybrid) does not need its batteries recharging, as they automatically capture energy usually lost under deceleration in a process known as regenerative braking, and it also has a generator which is activated when the petrol engine kicks in, supplying additional power either to the electric motors or to the batteries. It runs on electric power only at start-up and at very low speeds (i.e. in slow-moving and stop-start traffic in the city), and thus emits no harmful emissions at this point; the engine automatically stops and then re-starts itself when the RX comes to a halt, so it doesn't consume petrol whilst idling. The electric motors also assist the petrol engine when sudden extra bursts of acceleration are needed, and when the rear axle is activated, though for most mid- and high-speed cruising, i.e. on the motorway, it works in petrol-only mode like a 'normal' car.
The environmental benefits of the RX 400h are thus the most pronounced in city driving, which makes it ideal for buyers who are opting for a 4x4 for its image and high-riding stance, and who rarely venture into the countryside beyond the odd weekend picnic trip. Realistically, it is of little benefit to high-mileage motorway commuters, who are unlikely to see much by way of fuel savings, and overall, its abilities are a little limited; the battery range is relatively low, enabling it to travel only short distances in electric-only mode, and the extra weight of the hybrid powertrain, though much-reduced over that of earlier hybrid models, hampers the efficiency of the petrol powerplant when that is in action. A low-emissions, state-of-the-art diesel engine (using Toyota's Clean Power D-CAT technology, to feature in the Avensis and Lexus IS range) would consume less fuel overall, and emit less carbon dioxide, whilst still producing low levels of particulates and other harmful matter - and if it could run on organically-sourced biodiesel, it'd be the cleanest option of all.
The RX 400h is definitely a step in the right direction, as a means of introducing and refining future technology and raising public awareness of such advances if not a planet-saving device itself, but its largest benefit is really its feel-good factor. With the media, government and environmental organisations all fuelling a backlash against large, thirsty off-roaders bought by people who don't need to go off-road, buying an RX 400h is a way of making superfluous SUV ownership more publicly palatable. Its image-enhancing credentials also gloss over the fact that the RX is hardly the most dynamic drive whatever its powertrain, it's not a useful towing vehicle nor a mud-plugger by any stretch of the imagination, and despite an overhaul in 2003, it is now based on rather dated underpinnings.
The RX 400h is priced competitively against its fellow large luxury SUVs, with prices starting from £35,485 - not much for a vehicle with such complex technology. Many of its more conventional rivals are more accomplished all-rounders, however.
