Classy Mercedes plug-in is switched on

E300de is top class PHEV

The executive-level, high-end Mercedes E300de is a rare diesel plug-in hybrid.

Mercedes E300de
Rating	★★★★☆
Price	€62,720 - €70,839 as tested
Engine	a decent concoction
The Spec	thorough, but costly add ons
Verdict	best PHEV yet

The arguments for and against plug-in hybrid (PHEV) cars have had a long and fractious history.

Some factions say that the PHEV is the doorway to the inevitable electric future, as well as being a boon to company drivers, because of the lower benefit-in-kind taxes. 

Others say that the PHEV idea is already redundant.  The debate is not that simple.

There is plenty of in-trade evidence that while many companies have followed the ditch-diesel trend and opted for PHEVs, instead, for their fleet motors, their costs have increased because people have not been educated to drive the PHEVs properly, or at least not to extract maximum efficiency.

Further trade indicators  suggest that some individuals — as against fleet drivers — purchase these cars simply for their tax benefits and then never bother to charge them. This is quite commonplace, albeit not very sensible.

People who do drive them to extract maximum efficiency will find that, if fully charged, the  PHEVs can do most of their urban mileage on electric only and can then use the internal combustion engine for whatever other driving needs they might have.

The net difficulty with PHEV drivers who do not charge their vehicles, or otherwise extract the maximum from them, is that they leave the car's engine to hawk around a rather substantial amount of battery weight for little or no benefit.

But, as a majority of PHEVs are — by now — petrol-engined with an add-on electric system, rather than diesel, the actual efficacy of these systems is being called into question anyway. 

Manufacturers will — as manufacturers do — make claims about the consumption rates of these beasts.

England’s best-selling PHEV, the Mitsubishi Outlander,  has been hugely popular there. 

The Mercedes E300de plug-in hybrid has high-end interior materials and a quality finish.

But while the manufacturer might claim a potential return of 2.0 l/100km (139.7 mpg), drive it down a motorway with none of the electric apparatus running and I'm not sure you will get that. 

The thing here is, there are very few diesel-powered PHEVs around right now and  Volvo, Peugeot, and Audi stopped  making them when diesel sales  fell off a cliff.

One manufacturer has persevered, however, and that is Mercedes. 

And so, this week, we get to drive the new E-Class E300de, which is one of the very few diesel PHEVs available. And a classy thing it is.

We already know that the E-Class  is a very serious motor car, playing  at the top table in the luxurious, high-class executive market, but what of this, somewhat curious, variant?

Well — and I  don't place a lot of credibility in the PHEV genre  — it is a very decent contender and one  that will, undoubtedly, draw a small, but committed, number of buyers who are attracted not only by its tax-friendliness, but also by its genuine flexibility.

But what, exactly, is it?

Based on the hugely successful E220d model, the E300de shares the same basic, two-litre turbodiesel engine with 191bhp, but has added an electric motor that brings some 120bhp to the equation.

 That leaves total system output at a very healthy 305bhp and a whopping 700Nm of torque.

This, in turn, provides a top speed of 237kph and a 0-100kph time of 5.9 seconds, both figures, you'd have to admit, being quite impressive for what is nominally a diesel. 

Impressive, too, is the claimed economy figure of 1.4 l/100km (200 mpg), which, on the face of it, is quite staggering. The emission figure of 33g/km and the annual tax rate of just €140 are also eye-catching.

But even if you purchase this PHEV without ever intending to plug it in, an economy figure of 5.6 l/100km (50mpg) is not an unrealistic expectation. If you are careful to be fully charged at all times and you utilise the electronic systems to your maximum advantage, you will be able to see a figure in the region of 2.25 l/100km (124 mpg).

The electric-only range is a healthy 55km (well, healthy for the majority of PHEVs, anyway) and full charge can be achieved in five hours via a regular plug socket and in one-and-a-quarter hours via a 7.2 kWh wall-charger.

And the way the systems work means (unless you instruct it otherwise) the electric mode is the default and the diesel engine will only kick in when you either stomp on the accelerator for added zip (departing a junction) or when overtaking or climbing steep hills.

Refinement is an E-Class watchword and, by and large, that is the essence of this car, too, but the addition of electricity detracts from the driving pleasure. A lot of the time, you will be bolstered by the near-silence of the experience, but when the diesel kicks in, things can get quite raucous.

This is something of a Catch-22, because, usually,  this engine is one of the most refined of diesels, but when you get used to the noiselessness, the diesel doesn’t seem so refined after all. 

In fairness, however, that is being a touch picky.

On the road, the car is full of vim and vigour and while all that added battery weight (there's an  extra 350kgs here over the regular E220d) has shifted the dynamics a little away from the near-perfect balance of the regular diesel, it is still good in the handling and ride departments.

Like all brake systems that employ a regenerative characteristic, the brake pedal is a little on the numb side and takes a bit of adjustment. The battery installation has taken up a fair chunk of the boot, although capacity is still good.

In terms of the interior decor and the driver and passenger comfort, this E-Class is everything you would expect from a car with that name. 

The finishes are top drawer, the quality of the interior materials  is hugely impressive, and the amount of technology on offer is bang up to standard.

So, then, if utilised properly, the E300de can be a mile-munching economy fest, or an around-town cruiser  that uses no fuel at all.  It is certainly the most convincing PHEV I have yet encountered.

As someone who has consistently belittled PHEVs  for having little input into the future wellbeing of the globe, I found this one to be an excellent 'right-here-right-now' proposition.