This is a slightly bigger IS than we’ve been treated to before. The width may have grown by only 10mm, but there’s an additional 70mm in the wheelbase – 50mm of which is dedicated to the comfort of rear passengers.
The new, stiffer and slightly lighter bodyshell around it is a recognisable evolution of the previous-generation car’s. There’s Lexus's spindle-shaped grille up front and flared haunches to the rear, although it remains, at heart, an orthodox three-box styling effort.
Underneath, it diverges from convention somewhat. This is the first generation of IS to receive Toyota’s petrol-electric drivetrain. Rebadged as the Lexus Hybrid Drive, the system combines a 178bhp 2.5-litre petrol engine with a 141bhp electric motor.
The latter is part of a compact transaxle design that also houses the generator, a power split device (to combine power from the engine) and a reduction gear. Its nickel-metal batteries are stowed beneath the boot.
As with other Toyota hybrids, the water-cooled electric motor is capable of driving the rear wheels independently for short periods but usually works in tandem with the engine to provide drive. The Atkinson-cycle engine has been fettled for use in the IS300h, mostly with the intention of wangling improved efficiency from it.
Toyota (among others) believes that the greater natural efficiency of an Atkinson-cycle engine makes it the superior choice for use in a petrol-electric drivetrain. The IS300h’s four-cylinder unit is essentially a modified version of the conventional 2.5-litre motor that the manufacturer has been stuffing into RAV4s and Camrys destined for non-European markets.
For use in Lexus’s new saloon, Toyota has not only swapped out the camshafts and pistons to accommodate the asymmetrical compression and expansion ratios but also incorporated D-4S, the latest evolution of its direct injection technology.
With the help of higher-pressure injector nozzles and other detailed modifications, the compression ratio has improved to 13.0:1. Further efficiency gains have been made with a new exhaust gas recirculation system. Lexus also claims improved refinement thanks to the use of a low-friction timing chain and the optimisation of the balancer shaft.
Lexus also offers the more conventional IS200. It features a 242bhp 2.0-litre petrol and a six-speed automatic transmission, and will probably suit those seeking a smooth and familiar powertrain.