Mercedes-Benz CLS 450 2018 UK first drive

The shiny new Mercedes CLS has met with Mercedes’ shiny new mild hybrid drivetrain, with a real best-of-both-worlds brief.

The CLS 450 mixes a potent in-line six-cylinder twin-turbocharged 3.0-litre petrol engine with Mercedes’ new ‘EQ boost’ technology, comprising a 48V integrated starter generator and a lithium ion battery.

Sited between the engine and the nine-speed automatic gearbox (which drives all four wheels as standard), it not only provides the engine with an extra 22bhp and meaty 184lb ft of instant torque, but can completely switch the engine off in Eco mode when ‘sailing’, leaving the EQ boost to power the rest of the car’s ancillaries. Clever stuff.

The CLS 450 also presents our first chance to try Mercedes’ all-new big four-door coupé on the standard 19in alloy wheels filled with the noise-suppression foam, our earlier UK test being limited to the 400d version and its optional 20in wheels that made for a noisy and overly firm ride.

The model name of our CLS 450 test car may end in ‘AMG Line’, but it feels more ‘AMG Lite’ in the way the engine propels it down the road. This is a very quick car indeed, with excellent traction off the line and from low speeds from the four-wheel drive system.

It’s at low speeds when you really feel the extra shove of the 48V system, yet the way it blends with the engine is seamless. That’s also true when you select Eco from the driving mode selector toggle and the car enters its sailing mode; you don’t notice it, and there’s not exactly a sonorous engine note to miss anyway.

In-gear performance isn’t as razor-sharp as off-the-line performance, the nine ratios being better suited for efficiency than outright performance in the way they’re tuned in this car, nor does it ever sound as good as it should do.

It would also be wrong to call this an economical car with such force under your right foot — more economical than it would otherwise be is more accurate — yet it also shows the potential of such tech. Here, the 48V system is primarily used for performance, but you can see how it could also be used for a primarily fuel-saving purpose. The powertrain was first used in the S500 in a higher state of tune, so the drip down the range in different tunes and purposes is already occurring. The future’s well on its way.