Diesel motors have been gaining in popularity because they have been getting more powerful as well as more silent and refined. The Merc's updated 3.0-litre V6 takes this even further. The new diesel E350 CDI is so smooth and sweet-sounding even from the outside that anyone could mistake it for a petrol-powered car.

Mercedes engineers have taken what was already a very good motor and improved on it significantly. While much of the OM 624 (OM stands for Oil Motor or diesel) remains common with the previous-generation E280 CDI, Mercedes has both upped the power and improved fuel economy. In an effort to make it more refined and silent, the motor's compression ratio has been reduced significantly from 17.7 to 15.8. And there are new, more responsive injectors for better control as well as improved air flow and ducting in the engine, all of which translate to greater refinement.

This all-aluminium 72-degree V6 also makes commercial vehicles blush — producing 55kgm of torque from 1600rpm, just off idle, and this allows this otherwise heavy 1825kg car to be blown forward like it's one with the wind. Yes, it lacks the surge in power you get in the earlier 280 CDi and you miss that spike to a certain extent, but the overall performance is stronger.

Normal driving conditions call for only a gentle dab on the throttle; good enough to scoot forward in that effortless, well-insulated, typically Mercedes manner. The greater flexibility of the motor also means that the gearbox in ‘Comfort' setting can shift up gears much earlier, so progress is rapid and relaxed. However, with 231bhp, the sharp new E can easily be a performance saloon as well.

As you take off from rest with full throttle, the E-class's seven-speed automatic gearbox winds you through the gears in rapid succession, with the passengers happily pinned back in the seats. It takes a brisk 7.63 seconds to go from zero to 100kph. Performance continues unabated further up the power band as well, with 0-200kph coming up in 30.47 seconds. In comparison, the also very rapid 530d takes seven seconds to 100kph and 31.85sec to 200kph. The paddle shifts are really nice to use in both Sport and Comfort settings, the gearbox responding swiftly enough to requests for a downshift.

The Blue Efficiency badge you see on the wings of the car is not a single system, but rather a collection of optimisation measures that together make a significant impact on fuel economy. Our tests show the new E350 CDI is as efficient in the city and much more efficient than the E280 CDI on the highway.

The fresh styling with those crystal-cut headlamps and the sharp cuts along the body are fresh and modern and the new E sets new standards for refinement in this class. Even more impressive is the manner in which you step into the car, thunk the doors shut and leave the noisy world behind. It's like you've put on a set of ear muffs.

The new E-class's ride remains flat at any speed, with no big vertical movement even when poor roads are driven over at speed. The steering is quicker, the car feels much more agile and willing to take corners hard and after that initial bit of body roll, the frequency selective dampers firm up automatically when you drive harder. The earlier E had a more absorbent and silent ride at low speeds, and the new 350 diesel's rear seat comfort is not nearly as good. But the ride improves dramatically as speeds increase and there is additional room for rear seat passengers, which compensates to some extent. Smooth, super-refined, a pleasure to drive in our start-stop streets with massive performance waiting for your go, the new diesel motor complements the new E's character perfectly. It's all about the modern sharp-edged styling, the S-class-matching refinement on the inside, plenty of space comfort and quality, and dampers that provide a pliant ride or sharp handling automatically. Here is a Merc that upholds all the brand's traditional values of solid build, over-engineering and extreme refinement to the hilt, but like any modern car is also agile and fun to drive when you press on. True, some of the less important plastics in the cabin feel flimsy yet, that doesn't prevent the E350 CDI from recording a perfect score.

Technical Data

Fuel Diesel

Installation Front longitudinal

Type 6-cyls in Vee, 2987cc turbocharged, diesel

Bore/stroke 83.0/92.0mm

Compression ratio 15.8:1

Power 231bhp at 3800rpm

Torque 55kgm at 1600-2400rpm

Power to weight 126.57bhp per tonne

Torque to weight 30.13kgm per tonne

Transmission type Rear wheel drive

Gearbox 7-speed auto

Chassis & Body

Construction Monocoque, four-door saloon

Kerb weight1825kg

Wheels 8.5 J X 17 H2

Tyres 245/45 R17

Suspension

Front Independent, MacPherson struts with coil springs

Rear Multi-link, independent suspension with coil spring

Steering

Power-assisted, rack and pinion

Turning circle 11.25m

Brakes

Front Ventilated discs

Rear Ventilated discs

Anti-lock Yes

Keywords: diesel motorsMerc