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.