In-depth Reviews

Mercedes C 300 de hybrid

"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

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Owners Rating

3.5 out of 5

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Pros

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

Cons

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

While most manufacturers are moving away from diesel engines, Mercedes has spotted an opportunity. The result is this: the Mercedes C 300 de plug-in hybrid, combining the manufacturer's latest 2.0-litre turbodiesel engine with a sizeable battery pack and electric motor. In theory, this should give drivers the best of both worlds – long-distance cruising ability with impressive fuel economy, and the ability to complete many commutes using electricity alone with the resulting cost savings.

On a full charge, the C 300 de is capable of driving up to 35 miles before the diesel engine wakes up, and that includes the flexibility of an electric top speed of over 80mph, so it's not limited to town work. That electric range unsurprisingly gives the C 300 de stellar efficiency figures, so while its 188mpg maximum fuel economy should be taken with a pinch of salt, CO2 emissions of around 40g/km will be of most interest to company-car drivers, bringing down the cost of Benefit-in-Kind tax markedly.

Performance is boosted, too, thanks to the extra poke of the electric motor increasing overall power to 302bhp. That's enough shove to propel the C 300 de from 0-62mph in just 5.7 seconds. In normal driving, it doesn't feel like a rocket ship, because of the weight added by all the extra technology, and software designed to help you save fuel rather than burn it. There's even clever haptic feedback built into the accelerator pedal that pulses to warn you if depressing it further will summon the diesel engine.

Elsewhere, it's business as usual for the executive saloon and estate, with a well designed interior that treads a careful line between being stylish and functional. Trinkets include swish circular air vents and cool ambient lighting, while Artico leather seats and wooden trim remind you this is a cut above more mainstream models.

Diesel sales are dropping these days, but Mercedes could be on to a winner with the C 300 de. It'll especially appeal to the long-distance company-car drivers that form the C-Class' traditional core buyers.

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 188mpg, with CO2 emissions from just 39g/km – increasing slightly to 42g/km 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. Road tax will cost £130 a year – £10 less than a non-hybrid model.

A water-cooled on-board 7.4kW charger means the C 300 de can be topped up from around 10 to 100% capacity in 1.5 hours using a wallbox, 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 5.7 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 off energy recuperation and conventional brakes as you slow down.

Press the accelerator pedal hard and the diesel engine cuts in as revs increase, changing the noise inside audibly, but remaining 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; providing 'ECO Assist' tips and even haptic prompts through the accelerator pedal itself, encouraging you to maximise economy and EV driving. By vibrating the pedal, it lets the driver know more power is only available 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, but it's not yet known if the C 300 de will be available in SE, Sport and AMG Line trims, or be given its own separate equipment level.

Either way, it'll boast one of the best designs currently available, with 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 setup 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 be too much of a cause for concern.

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.

Price, value for money & options

If the price is right, low running costs will make the C 300 de very appealing

While we've had a first taste of the C 300 de in Europe, it's not expected to go on sale in the UK until mid-2019. When it does, prices are estimated to start from around £36,500 after the government's plug-in car grant has been deducted. This should place it in contention with some diesel rivals, while offering the advantages of far cheaper BiK and running costs.

Options are likely to stick close to diesel version of the C-Class, where a Premium package adds upgrades including a 12.3-inch digital instrument panel, ambient lighting, online services, adaptive LED headlights and wireless smartphone charging for around £2,800. A Premium Plus pack includes the above and a helicopter-view camera, Burmester audio system, keyless entry and panoramic sunroof for £5,000.

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