Road Test: Mercedes-Benz S Class S300L BlueTEC Hybrid AMG Line 4dr Auto

A hybrid Mercedes S-Class sounds like a posh Prius...

Far from it, actually, although the drivetrain doesn't sound very S-Class. This S300 gets a 2.1-litre four-cylinder diesel engine, with a small electric motor sandwiched between the engine and seven-speed automatic gearbox. Drive is to the rear, naturally.

A four-cylinder diesel in an S-Class?

Before we get to the thorny issue of a four-pot diesel in the car upon which Mercedes's reputation is built, let's get the numbers out of the way. The engine pumps out 201bhp, the motor another 27bhp, and in a car weighing 2035kg, it's a minor miracle that it'll accelerate from 0-62mph in 7.6secs and onto a top speed of 149mph.

And the ‘hybrid' part of the equation?

As long as there's enough juice in the battery, you push off on electric power with the diesel chiming in once you need a bit more oomph. Then once up to a constant coasting speed, it'll automatically switch the engine off, and glide around on electric power alone. It's seamless.

I'm guessing it's frugal, then

It's witchcraft. This big, luxurious Mercedes barge emits just 120g/km of CO2 and sips a claimed 61.4mpg on the combined cycle (we saw 44.1mpg on our run). It's the most frugal and environmentally friendly S-Class Merc currently builds.

Wow. But do S-Class buyers really care about numbers like this?

When you're only paying £30 a year in road tax and can get up to 944 miles on a single tank, somebody cares. And, aside from that, our only gripe with this car is the gruffness of the four-cylinder. It's hugely impressive, but under hard acceleration, the engine makes its presence felt more than you'd like, because you're in an S-Class. But that's about it.Pace is never an issue - you're not going to be drag racing an S-Class unless you're a sadist or you have an S63 - that drivetrain offering up punch rather than thunder. You're never left wanting, however, and the usual S-Class dynamic nuances apply: gorgeous ride, light steering.

How much is it?

A whopping £72,260, which is just under 10 grand more than the non-hybrid, faster and more powerful V6 diesel S350 BlueTec. The other hybrid, the S400 AMG L (petrol V6, electric motor, 302bhp), costs £74,930.