Mercedes S400 Hybrid (2009) CAR review

Mercedes always strives for its S-class to be at the technological cutting edge, so it must have been pretty miffed when Lexus beat it to market with its S-rivalling, hybrid-powered LS600h. This, then, is Mercedes’ riposte: the S400 Hybrid.

Brilliant, an S-class hybrid! When do I get mine?

Ah. Yes. Thing is, you won’t, not unless you steer from the left. The Germans won’t invest in right-hand drive production, pointing out that 80% of Brits will take the 350 CDI, while the Japanese often order S-classes in left-hand drive anyway because, for some reason, many see it as more prestigious. As for the poor Australasians and South Africans – well, they weren’t even mentioned.

Whatever the story, I’d say we’re being short-changed, and that the 80% of Brit diesel buyers would be equally – if not better – served by the S400 hybrid. Seeing as I’ve been something of a hybrid cynic in the past, that’s saying something.

Calm down, calm down... Give me the tech story, first

The new Merc S400 Hybrid uses the 3.5-litre V6 petrol that’s familiar from the C-, E- and S-class 350s. The units aren’t straight swaps, however, the 400 receiving revised cylinder heads, pistons, camshafts and more as well as the hybrid gubbins.

The seven-speed auto gearbox is the same one used throughout the range, but the lithium-ion hybrid unit is neatly integrated with it. It’s a relatively compact installation that’s designed to last the life of the car, but it does add 75kg over the non-hybrid petrol.

However, horsepower goes up, the hybrid adding a 20bhp hit to the 275bhp engine, and serving up an impressive 118lb ft from standstill. That helps combat the weight gain, plus lower C02 emissions by 21% compared with the regular petrol S350 – and it deliver 8mpg more.

Best of all, the mpg and C02 compare very favourably with the diesel, the hybrid turning in 35.8mpg to the diesel’s 37.2mpg and churning out just 186g/km versus the diesel’s 199g/km. And that, points out Mercedes, is cleaner and more frugal than the big – and, don’t forget, more powerful, larger-lunged – Lexus.

>> Click 'Next' for more of CAR's road test review of the Merc S400 Hybrid