From £29,0358
Combination of a diesel engine and electric motors makes the C300de hugely capable in all environments

Our Verdict

Mercedes-Benz C-class

Can the C-Class, our perennial runner-up in the compact saloon category, finally reach the top spot?

Simon Davis
9 October 2018

What is it?

There’s an incredibly strong chance that Mercedes-Benz might just be on to something big with its new C300de.

You’ll be well aware of the battering diesel cars have been subjected to over the past 18 months or so. Both government and mainstream media have increasingly been pushing the idea that oil-burners are bad news for the general public’s health - particularly in busy city centres - despite the fact that any automotive engineer worth their salt will tell you that the latest diesel engines are cleaner, less polluting and more efficient than ever before.

But what if your diesel car was capable of running on nothing but electricity in these built-up areas? And what if, once you’ve left the confines of the urban sprawl, you could rely on the superior range, low CO2 emissions and effortless torque of its engine to get you to your final destination, free from any associated guilt about your choice of powerplant?

That, essentially, is exactly what the C300de sets out to allow you to do.

Like any other plug-in hybrid, it combines an electric motor – here capable of running the car on electricity alone for around 30 miles, courtesy of a 13.5kWh battery – with an internal combustion engine. Unlike in most other plug-in hybrids, though, that engine is fuelled by diesel.

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It’s a 2.0-litre, four-cylinder unit that develops 191bhp and a reasonably meaty 295lb ft of torque. The electric motor, on the other hand, makes 121bhp and 325lb ft. Combined, they give the C300de 302bhp, while torque has to be limited to 516lb ft, most likely so as to not overwhelm the nine-speed automatic gearbox.

Not only does this allow Mercedes to make the rather impressive claim that, in the estate guise you see before you, the C300de will be able to do 0-62mph in just 5.7sec, but also that it should also be capable of achieving an average fuel economy figure of 177mpg and CO2 emissions as low as 42g/km, albeit under NEDC conditions.

Now, plug-in hybrids have been making similarly impressive economy claims for some time. And while they might be able to rely on their ability to travel on electricity alone to bring down their consumption and emissions figures in the city, show one a prolonged stretch of motorway and chances are its petrol engine will struggle to return a figure that’s anywhere near those on-paper claims. The Range Rover P400e, for instance, can supposedly manage 101mpg, but I spent a day in one a few months back and the best figure its trip computer could conjure was 23mpg.

Anyway, while some scepticism is always recommended when looking at these things, the point is that the C300de, with its ability to switch to diesel power at the drop of a hat, should be able to come much closer to matching those claims than its petrol-powered contemporaries.

What's it like?

The car certainly made a good effort of it on the test route around Stuttgart, which combined plenty of time in heavy stop-start inner-city traffic with a few stints at speeds closer to what you’d be doing out on the motorway.

While it didn’t manage that hallowed 177mpg figure, its trip computer was still showing an average consumption figure of around 90mpg at the end of the route. That was with the diesel engine being the sole source of power for a good proportion of the total trip, too.

However, while it proved to be impressive from an economy point of view, it’s not an engine you’d be willing to label a glowing example of refinement. While there are certainly diesel units out there that are far gruffer, the C300de’s has a distinctly agricultural edge to its timbre when under load. Even at a steady cruise, its humming away in the background was noticeable, although admittedly I may have become more sensitive to any sound it made after an extended period of running about on battery power alone.

The manner in which the two engines work together is impressive, though. Leave the C300de in its standard Hybrid driving mode and the electric motor provides smooth, linear acceleration off the line. Take off with a bit more urgency and the diesel engine will step in in a largely seamless fashion, with both motors providing that sizeable slug of low-down torque to get the car up to speed in very swift fashion indeed.

The auto ‘box works well, too: you largely won’t notice it working away to swap cogs under the more laid-back driving style that our busy urban route demanded, although whether the same would be true if you were to drive with a degree more enthusiasm, I’m unable to say.

As for the way the C300de rides, it’s a bit of mixed bag. It's certainly a comfortable car; there’s tight, pliant body control here that allows it to deal with undulating surfaces with plenty in the way of confidence. But lumps, bumps and other imperfections in the road’s surface make it lose a touch of its composure, at times giving the impression that it's stumbling over, rather than ironing out, these less-than-stellar patches of Tarmac.

Body roll through tighter corners is well managed, too, and the steering, while not exactly bristling with feel, is pleasingly direct and nicely weighted.

The interior, meanwhile, maintains the same sense of opulence that is common to all C-Classes'. Ambient lighting and wood panelling look the part, although the latter does feel a bit disappointing to the touch, while the leather seats of our test car were both comfortable and supportive.

The C300de goes without the new dual-screen dashboard layout of the new A-Class, though, and its system, while easy enough to operate, isn't the slickest system on the market - particularly next to those offered by Audi and BMW. In a general sense, though, you’re in no danger of feeling short-changed.

Should I buy one?

With the mid-2019 launch of the C300de still some way off, prices are yet to be announced, although I’m not hugely confident that they’ll be particularly cheap. The regular C300d Estate will set you back at least £41,400, so I don’t think it’d be entirely unfair to presume this new diesel-electric variant will likely add at least a few thousand pounds on top of that figure.

This will likely mean that the C300de will only make financial sense for a reasonably small number of rather deep-pocketed individuals who know they’ll likely cover a fairly high number of miles on an annual basis. But that’s generally the case with diesel-powered cars anyway, isn’t it? Yes, they don’t make sense for the driver that’s only ever going to use one for the school run or the morning commute, but there are those who benefit from them greatly.

If combining a diesel engine with an electric motor goes some way to reversing the damage that’s already been done, surely that’s a good thing.

Mercedes-Benz C300de Estate specification

Tested Germany Price £45,000 (est) On sale Summer 2019 Engine 4cyl, 1950cc diesel with electric motor Power 302bhp (combined output) Torque 561lb ft (combined output) Gearbox 9-speed automatic Kerb weight na Top speed 155mph 0-62mph 5.7sec Fuel economy 176.6mpg CO2 42g/km Rivals BMW 330e, Volkswagen Passat GTE

Join the debate

Comments
24

10 October 2018

The first line in this article gives the impression that this video the first diesel hybrid car put into production when it's not even the first Mercedes diesel hybrid and Volvo offers a diesel hybrid as well.

That said it's the perfect combination for my driving but for 75% of drivers a pure EV or petrol hybrid will be perfectly adequate.

10 October 2018
Autocar wrote:

... There’s an incredibly strong chance that Mercedes-Benz might just be on to something big with its new C300de...

Why is the this strong chance 'incredible'?

10 October 2018

The problem Mercedes have with this Diesel Hybrid, like Land Rover did when they built one, is that most people who want a hybrid for environmental reasons (rather than a tax break) don't want a diesel. Maybe it is just to appeal to those looking for tax breaks.

10 October 2018

Really. All these arguments about how fuel usuage should be measured and we come up with figures like this, it's not that far behind the pure LEAF EV, crazy EU.

All you need to know is 'do Hybrids pay for themselves' opposed to pure diesel or petrol. In the case of the Pirus the answer seems to be yes but if it only improves your total mpg (factoring in including plugged-in electricity) by 25% then it's probably not if that battery/motor adds £4000 to the price (environmental issues aside).

typos1 - Just can’t respect opinion

10 October 2018

Yes, new diesels are much cleaner, but that is because they have so much emission equipment strapped to them that they are no longer a good bet for reliability, Ultimately, this car is pointless. You have a unloved potentially unreliable Diesel engine with an electric motor added to it. It will be over the £40k tax barrier, so makes little economic or environmental sense,

10 October 2018
Broughster wrote:

Yes, new diesels are much cleaner, but that is because they have so much emission equipment strapped to them that they are no longer a good bet for reliability, Ultimately, this car is pointless. You have a unloved potentially unreliable Diesel engine with an electric motor added to it. It will be over the £40k tax barrier, so makes little economic or environmental sense,

You seem to be unaware that petrol engines also have loads of emissions equiment strapped to them too - complex 3 way closed loop catalysts and from this year particulate filters. Diesel hybrids make a lot of environmental sense, second only to electric cars.

XXXX just went POP.

10 October 2018
typos1 wrote:

Broughster wrote:

Yes, new diesels are much cleaner, but that is because they have so much emission equipment strapped to them that they are no longer a good bet for reliability, Ultimately, this car is pointless. You have a unloved potentially unreliable Diesel engine with an electric motor added to it. It will be over the £40k tax barrier, so makes little economic or environmental sense,

You seem to be unaware that petrol engines also have loads of emissions equiment strapped to them too - complex 3 way closed loop catalysts and from this year particulate filters. Diesel hybrids make a lot of environmental sense, second only to electric cars.

Not all petrol engines have or will have a GDF (far simplier than a DPF anyhow). They don't have a complicated Urea injection system, as much sound or vibration killing material or an expensive DPF.  Oh in the case of the best Hybrid, a petrol Prius, it doesn't need a turbo to pull away.

Which explains to some extent why they're more expensive.

typos1 - Just can’t respect opinion

10 October 2018

Which explains to some extent why the 'Diesel' option is more expensive

typos1 - Just can’t respect opinion

10 October 2018

Yes, new diesels are much cleaner, but that is because they have so much emission equipment strapped to them that they are no longer a good bet for reliability, Ultimately, this car is pointless. You have a unloved potentially unreliable Diesel engine with an electric motor added to it. It will be over the £40k tax barrier, so makes little economic or environmental sense,

10 October 2018

I really don't like them calling a rattling 2.0 4 cylinder engine a '300'. 

 

Whether petrol or diesel, it it just isn't a 300, and calling it that draws attention to the fact.

 

 

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