Mercedes S400 Hybrid: Test Drive Review

Mercedes’ new S-class luxury saloon comes with a petrol-electric hybrid version alongside traditional petrol and diesel alternatives.

Interestingly, there’s just 1g/km of CO2 between the diesel and petrol-electric hybrid powertrains, and both are impressively under 150g/km, although the hybrid is £4000 more expensive and 75hp more powerful.

There’s a 5.6mpg difference in the official economy figure in favour of the diesel, but the hybrid’s 44.8mpg for a near two-tonne luxury saloon capable of a speed-limited 155mph still shows how far the industry has come.

The hybrid is also 4.6 percentage points worse off from a residual value perspective, as the S350 CDI achieves a peerless 34.0% RV, while BMW, Audi and Lexus rivals can’t even match the Merc hybrid’s 39.4%, although the BMW 7-series Active Hybrid runs it close.

That means the S350 diesel is 10.1p per mile cheaper to run than its sibling; however, it’s also worth remembering there’s a plug-in S-class with figures of 69g/km and 94.2mpg coming in autumn 2014.

The outgoing S-class was the sector-leading luxury model, and the new model is another step forward in class, refinement and quality. 

The hybrid system works well at low speed and is capable of significant zero-emission running, but does have the occasional habit of being more jerky than one might expect of an S-class if the driver changes throttle pressure too quickly when the car’s switching from petrol to electric mode.

But for elegant arrivals, whistling noiselessly to a standstill beats the admittedly refined diesel clatter. 

The S-class is still an epically desirable tool, and this hybrid makes it an interesting choice compared with the diesel, probably shading it for heavy city use, but being less logical if longer runs are more likely.