Interesting quote from Lexus GS chief engineer Yoshihiko Kanamori in this Autocar article:
Referring to the new four-cylinder Audi A8 hybrid, Yoshihiko Kanamori, chief engineer said that the need for in-cabin noise cancellation to improve refinement in the German car was one of the reasons that a Lexus GS ‘could never have a four-cylinder engine.’
Although the Japanese company would not reveal more about the new GS Hybrid (potentially badged GS350h) it is possible that it will use a version of the 204bhp 2.5-litre V6 engine that is fitted to the new GS250.
This puts an end to the idea that this second GS hybrid will share the 2.5L 4-cylinder engine found in the new ES 300h — in fact, it appears that an all-new V6 hybrid powertrain is on its way to the Lexus lineup.
This openness to share information is a new tactic from Lexus, and leads to all sorts of speculation — will the new V6 hybrid be based on the existing 2.5L V6 in the GS 250 or an entirely new engine? Will it debut in the GS or the third-generation IS?
Autocar mentions one expected milestone:
Hitting a CO2 figure of 119g/km – matching the BMW 520ed – is the likely aim of the new model. It would, though, also offer higher performance than the four-pot BMW.
I would add one more fairly obvious point — it has to beat the Lexus GS 450h’s fuel economy by a decent margin (the GS 450h is currently rated at 31 combined MPG in the USA, 5.9l/100km in Europe).