New Mercedes E 300 de 2019 review

We drive the new Mercedes 300 de to see if the diesel-electric hybrid works just as well as its petrol-electric sibling...

Overall Auto Express Rating

4.0 out of 5

The E 300 de is a very worthy alternative to the petrol-electric E 300 e. It matches that car’s Benefit-in-kind company car tax rate, but while the petrol hybrid is a slightly better option around town, the E 300 de mixes similar pure-electric capacity with the long-distance cruising strengths of a diesel. We suspect it’ll be more economical in the real world as a result, bringing down running costs to really appealing levels.

Mercedes certainly isn’t holding back on electrification. The company’s pure-electric EQ sub-brand is only a few months away from launching its first model. And stalwarts in the regular line-up are getting more volts too; we recently tried the E 300 e petrol-electric hybrid in the UK, and now it’s time for us to sample its diesel sister, the E 300 de.

The mechanical make-up is a mixture of proven engines and new electric tech. The E 300 de’s combustion engine is the same 2.0-litre, four-cylinder unit that you’ll find in an E 220 d; it delivers 191bhp and 400Nm of torque. But alongside it, there’s an electric motor bringing an additional 121bhp and 440Nm.

• Best plug-in hybrids to buy

Together, the two units combine to produce a system maximum output of 302bhp and 700Nm; the peak power outputs of the units are not delivered at the same time.

The car’s 13.5kWh battery has big enough reserves, Mercedes claims, for the E 300 de to travel up to 34 miles on electric power alone, and at decent speeds too. On one of the faster 7.4kW household points, a full recharge takes less than two hours. So it’s feasible that someone with a modest commute could plug their car in every night - or every other night - and not use a drop of fuel during the working week. Incidentally, you can have the E 300 de as an estate - but your electric-only range will take a slight hit, dropping to 32 miles.

These numbers - and official CO2 emissions of as little as 41g/km, even on the tougher WLTP cycle - make for attractive reading when they’re translated into a Benefit-in-kind tax rate of just 13 per cent. And while lots of petrol-electric hybrids fall short of their promise on the open road, the E 300 de keeps its word more effectively.

That’s mainly due to the diesel engine, which has enough low-down shove in its own right to cope with a car of the E-Class’s size. This means that, even with the extra weight of the batteries on board, you can cruise along using nothing but the diesel engine and happily return north of 50mpg.

While you’re doing this, you can use the E 300 de’s mode switch to maintain the level of charge in the batteries (or to replenish it, if so required). And then when you do get to the end of the motorway and enter a city centre, you can flick the switch to run on electricity alone.

It’s a shame, of course, that the car isn’t quite intelligent enough to work this out for itself. Hybrid mode still improves on the diesel-only economy, of course, and the transition between electrical assistance and combustion engine is managed with impressive smoothness – helped by the well-integrated nine-speed automatic transmission.

Frankly, you could leave it in this setting all day long and not be that aware that you’re driving a plug-in hybrid at all. Some of those who choose the E 300 de for its company car tax breaks may do exactly that - although they’ll be missing out on some potentially stellar running costs as a result. It’s a doddle to plug the E 300 de in, too, thanks to a neat charging socket integrated into the rear bumper. 

Hybrid buttons aside, there’s little in the cabin to set the E 300 de apart from its conventionally powered stablemates. But that still means you get a pleasing mix of premium finishes and materials, as well as one of the best infotainment systems in the business - and an extravagant widescreen display in the fascia.

There’s room on board for four grown-ups to travel long distances in comfort, too - and the E 300 de’s relaxed chassis settings should help with this. The car’s extra weight has resulted in a slightly firmer ride, but in the most part this remains a car gloriously focused on comfort, not handling agility. If you want a hybrid executive saloon to thread down a B-road, a (petrol-electric) BMW 530e will still be a better companion. But with only really sharp imperfections getting through to the E 300 de’s cabin, it seems very well suited to that mixture of urban EV running and diesel long-leggedness.

You do pay a penalty in boot capacity, of course; there’s a step in the floor that restricts the height of items that you’re able to slide ride into the load bay, and you lose more than 100 litres compared with a normal E-Class. But for most uses, even this compromised set-up should be fine, with enough space for a couple of decent-sized suitcases and an overnight bag.

Most Popular

Driving test update to preserve the manual gearbox
Dacia Duster gear lever
News

Driving test update to preserve the manual gearbox

With more drivers learning in autos and electric cars, the DVSA is looking to update the driving test so people can still drive manuals in future
16 Jun 2021
Tesla Model 3 police car all set for evaluation by UK emergency services
Tesla Model 3 police car - front
News

Tesla Model 3 police car all set for evaluation by UK emergency services

Tesla hopes to offer UK police forces a new zero-emission emergency responder option with the Model 3 police car
17 Jun 2021
New 2021 Vauxhall Astra to offer plug-in hybrid power
Vauxhall Astra render
Vauxhall Astra

New 2021 Vauxhall Astra to offer plug-in hybrid power

The new Vauxhall Astra will get a plug-in hybrid powertrain and a more premium image - here’s how it could look
17 Jun 2021
Ineos Grenadier prototype 2022 review
Ineos Grenadier prototype
Ineos Grenadier 4x4

Ineos Grenadier prototype 2022 review

Can the Ineos Grenadier really fill the mud-splattered void left by the old Land Rover Defender? We take a first drive in a prototype to find out...
15 Jun 2021
Motorists think they can get away with driving offences due to lack of road police
police speed gun
News

Motorists think they can get away with driving offences due to lack of road police

Lack of road traffic police officers in the UK is making it easy for drivers to break the law, according to a survey of 15,500 British motorists
16 Jun 2021
New Nissan Qashqai 2021 review
Nissan Qashqai 2021
Nissan Qashqai

New Nissan Qashqai 2021 review

We get behind the wheel of the larger, more comfortable and higher-tech Nissan Qashqai SUV in the UK
16 Jun 2021
New Audi Q4 e-tron 2021 review
Audi Q4 e-tron 2021  front
Audi Q4 e-tron

New Audi Q4 e-tron 2021 review

We get involved with the new all-electric Audi Q4 e-tron SUV on UK roads for the first time
17 Jun 2021
Dacia unveils new badge design
Dacia badge
Dacia

Dacia unveils new badge design

The new Dacia branding will feature on the company’s cars from 2022, with the Bigster being the first candidate
17 Jun 2021
UN report highlights ethical problems with electric cars
Electric car charging
News

UN report highlights ethical problems with electric cars

Analysis reveals lithium refining takes 65 per cent of Chilean region’s water, while 40,000 child miners dig for cobalt in DRC
14 Jun 2021
'I was cynical about Hyundai's aim to be the world's 2nd biggest carmaker, not now'
Opinion Genesis Hyundai Ioniq
Opinion

'I was cynical about Hyundai's aim to be the world's 2nd biggest carmaker, not now'

Steve Fowler is impressed by Hyundai's electric cars, its N division and now its luxury Genesis brand
16 Jun 2021
Fan-designed Ford Puma ST Gold Edition revealed
Fan-designed Ford Puma ST Gold Edition
Ford Puma

Fan-designed Ford Puma ST Gold Edition revealed

Ford unveils a special edition Puma ST, with a black and gold colour scheme chosen by Ford fans over social media
18 Jun 2021
Mazda to launch 10 new hybrids and three new EVs by 2025
Mazda electric plan
Mazda

Mazda to launch 10 new hybrids and three new EVs by 2025

The electrification push forms part of Mazda’s goal to become a completely carbon neutral company by 2050
17 Jun 2021
New Renault Arkana 2021 review
Renault Arkana - front
Renault Arkana

New Renault Arkana 2021 review

Does an eye-catching coupe-SUV body give the new Renault Arkana the edge over other mid-size SUVs? We find out...
16 Jun 2021
New Skoda Enyaq iV 2021 review
Skoda Enyaq iV 80 Sportline - front
Skoda Enyaq

New Skoda Enyaq iV 2021 review

The new Skoda Enyaq iV is the Czech firm’s first bespoke electric car and we've tested the full range on UK roads
10 Jun 2021