In-depth reviews

Mercedes C 300 de hybrid review

"The Mercedes C 300 de bucks the trend by pairing plug-in hybrid technology with a modern diesel engine, to great effect"

Carbuyer Rating

4.1 out of 5

Owners Rating

3.5 out of 5

Read owner reviews

Pros

  • 35-mile EV range
  • Long-distance ability
  • Solid performance

Cons

  • Infotainment could be slicker
  • Battery pack adds weight
  • Pricey options

Diesel might be a dirty word for many people, but it can still provide very strong fuel economy – and Mercedes is one of the few makers to employ this fuel in a hybrid car. The Mercedes C 300 de plug-in hybrid uses a modern 2.0-litre diesel engine with its battery and electric motor, which can give the best of both worlds – zero-emissions driving at low speeds and in town, then high-efficiency running on the motorway with the engine on.

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The C 300 de can drive for around 35 miles at up to 80mph without even turning the engine on, which is slightly above average for this kind of car. Fuel economy isn’t too useful to refer to (at 235.4mpg) because it really depends on how you use the car and when you can charge it up. What’s more important is the CO2 emissions of 31g/km, which mean it’s a very affordable vehicle to run in terms of company car tax.

The total power output of the engine and electric motor is a healthy 302bhp. This means it’s a quick car – 0-62mph takes 5.6 seconds – and is relaxing to drive because you’ve got plenty of overtaking potential under your right foot. You can even decide whether or not to wake the engine, because the pedal has a noticeable step in its travel. Go beyond this and the engine comes on, providing full power.

Meanwhile, the rest of the C 300 de is the same as in other models in the C-Class range, which is definitely a good thing. The interior is very smart, with high-quality materials, plenty of space and loads of modern and hi-tech equipment.

The C-Class is comfortable and good to drive, with a smooth gearbox and quiet running especially at low speed. It’s a fantastic option for those who need a company car that’s cheap to tax but who also need the ability to drive efficiently for long distances.

MPG, running costs & CO2

Very cheap to run if you can charge it regularly

While rival manufacturers including Lexus and Volvo concentrate on petrol hybrids, Mercedes is keen to offer motorists a wide choice of powertrains, including this diesel C 300 de plug-in hybrid. Later, it’ll be joined by a petrol C 300 e version.

Its 13.5kWh battery pack and electric motor are good for an impressive zero-emissions range of up to 35 miles, making it possible for many owners to charge it overnight and cover their daily commute without using a drop of fuel. With a top speed of more than 80mph possible before the diesel engine chimes in, this could even include a quick stretch of motorway or dual-carriageway driving.

Official tests from the outgoing NEDC testing procedure give the C 300 de fuel-efficiency figures of up to 235.4mpg, with CO2 emissions from just 31g/km – increasing slightly when larger alloy wheels are fitted. Fuel economy will, of course, vary wildly depending on how owners charge and drive the C 300 de, but company car drivers are sure to be drawn to its low Benefit-in-Kind (BiK) band. VED (road tax) will cost the discounted rate each year.

A water-cooled on-board 7.4kW charger means the C 300 de can be topped up from around 10 to 100 per cent capacity in 1.5 hours using a wall box, or around five hours from a domestic socket.

Engines, drive & performance

Mercedes has done a great job of smoothly blending electric and diesel power

Adding plug-in hybrid technology to the C-Class doesn’t just make it cheap to run; it’s surprisingly rapid, too. Mercedes’ latest 2.0-litre diesel engine and electric motor combine to produce 302bhp. This cajoles the C-Class from 0-62mph in just 5.6 seconds and on to a limited top speed of 155mph.

You wouldn’t necessarily know it while gliding around town in near silence, with just a faint whine from the motor and gearbox. Apart from the slightly sudden take-off from standstill, it’s an impressively relaxed experience, and Mercedes has found a good blend between the feeling of energy recuperation and conventional brakes as you slow down.

Press the accelerator pedal hard, and the diesel engine cuts in as revs increase. While this audibly changes the noise inside the cabin, the car remains just as refined as a regular diesel C-Class fitted with the same engine. The weight of the electric motor and battery pack does take its toll on performance, though, so the C 300 de doesn’t feel quite as fast as its on-paper figures.

It urges you to drive efficiently, too, but providing ‘ECO Assist’ tips and even haptic prompts through the accelerator pedal itself, all encouraging you to maximise economy and EV driving. By vibrating the pedal, it lets the driver know more power is available only by firing up the diesel engine.

Interior & comfort

The Mercedes C-Class' interior is top drawer, but its infotainment system already feels slightly dated

The plug-in hybrid version of the C-Class shares its interior with the rest of the range, and comes in Sport Edition, AMG Line Edition and AMG Line Night Edition trims. Equipment is good, including sat-nav, LED headlights, 12.3-inch digital dash, 10.25-inch central screen, heated leather seats, AEB and cruise control.

It uses upmarket materials, classy ambient lighting and standard Artico leather seats. For the facelift, the central infotainment screen was joined by a digital instrument cluster sitting behind the steering wheel, but it’s not quite as slick as the dual-screen set-up found in the latest Mercedes A-Class. In the C 300 de it is, however, also possible to delve into information about the hybrid powertrain, charging status and so on.

Practicality & boot space

Lots of passenger space and an estate version make the Mercedes C 300 de a sensible option

If you need a plug-in hybrid that’s also practical, you’re in luck, because along with the various SUVs offering the technology the C 300 de also boasts plenty of space and is available as both a saloon and estate.

There’s plenty of room for adults in the front and rear seats, with more space between the front and rear wheels than in older C-Class models. The standard C-Class Estate has a 490-litre boot (with the rear seats up), stretching to 1,510 litres with them folded flat. Mercedes has yet to release figures for the plug-in hybrid, but it’s possible the boot could be slightly smaller due to the battery pack and electric motor.

Reliability & safety

Mercedes is investing heavily in plug-in technology

The Mercedes C-Class has a long lineage and reputation for being solid and well engineered. The brand is also well on its way to becoming an established electrified-vehicle manufacturer, so its plug-in hybrid technology shouldn’t give too much cause for concern. However, the C-Class came in 71st out of the top 75 cars in our 2021 Driver Power survey.

It should also be extremely safe, with a wealth of safety equipment and crash know-how poured into the popular model. The C-Class has already been awarded five stars from independent crash-test body Euro NCAP, and along with seven airbags, there are systems designed to avoid or mitigate collisions.

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