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Mercedes-BenzS-class Hybrid (2014-2018)

Large
Plug-in hybrid (PHEV)
Used only

£18,605Typical price

Test score

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On paper it looks almost too good to be true: a powerful luxury saloon with a fuel economy of more than 100mpg and CO2 of just 65g/km. At least, those are the claims for the Mercedes-Benz S500 Plug-In Hybrid, the petrol-electric hybrid version of the S-Class, launched in 2014. Are these claims borne out? Read our full road test review to find out.

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cons

What's included?

What is it?
What's it great at?
What's it like to drive?
How reliable are Mercedes-Benz's cars?
How comfortable and spacious is it?
How economical is it to run?
How safe is it?
Is there anything I should look out for?
Should I buy it?

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KEY TEST RESULTS
Comfort and practicality
Brand reliability 0-4 years

Jan 2023Last checked by Which?
Jul 2017First reviewed by Which?
Sept 2014Released

The overall Which? test score is made up of the following star ratings, all determined by our rigorous lab tests.

How we test cars

6 Jun 2025

Ease of driving

Overall
Visibility
Smoothness of power delivery
Driving stability
Cabin layout

How we test ease of driving

To find out how easy a car is to drive, we assess cars across a number of areas from visibility and handling to the layout of the cabin and how smoothly the engine delivers its power.

Performance

Overall
In-gear acceleration
Brakes

How we test performance

We test braking distances and whether the effectiveness of the brakes fade with repeat use. Performance is based on in-gear acceleration.

Comfort and practicality

Overall
Entry and exit
Seat comfort
Ride quality
Quietness
Seat space
Boot space (large cars, SUVs and MPVs)

How we test comfort and practicality

Comfort and practicality includes how easy it is, or not, to get in and out of the car and the maximum height of occupants. We also measure road, wind and engine noise and assess how well the car deals with bumps from large potholes to jittery surfaces like cobble stones.

Safety kit

How we test safety kit

We factor in the safety equipment that’s factory-fitted or optional, along with how well the car protects its occupants and pedestrians in the event of an accident. We also test how easy it is to fit a variety of child car seats.

Brand reliability 0-4 years

Overall
Electric car reliability
Plug-in hybrid reliability
Petrol reliability
Diesel reliability

How we test brand reliability 0-4 years

Our reliability ratings are based on the feedback from tens of thousands of UK motorists, as collected in our annual Which? car survey. We divide all reliability feedback into three age groups: cars aged up to four years, five to nine years, and 10 to 15 years.

Brand reliability 5-9 years

Overall
Diesel reliability

Brand reliability 10-15 years

Overall
Petrol reliability
Diesel reliability

General
Class	Large
Luxury	Yes
Convertible	No
Availability	Used only
Used price	£18,605 - £36,120
Fuel type	Plug-in hybrid (PHEV)
Tested fuel efficiency	54.3mpg
Length	5,246mm
Width (excluding wing mirrors)	1,899mm
Width (including wing mirrors)	2,135mm
Height	1,496mm
Driver max height
Second-row passenger max height
Boot space with seats up
Boot space with seats down
Number of seats	5
Folding rear seats	No
Isofix attachments	Yes
Turning circle	12.25 m
On sale date	21 July 2017
Lowest pence-per-mile cost	£11.21

Latest tested engine
Engine and trim name	S 500 PLUG-IN HYBRID long 7G-TRONIC PLUS
Fuel type	Plug-in-Petrol-Hybrid
Capacity and power	3-litre (442hp)
Transmission	7-speed automatic
Driven wheels	Rear-wheel-drive (RWD)
Fuel tank capacity	70 litres
Tested fuel economy: City / Out of town / Motorway (mpg)
Tested fuel economy: Combined (mpg)
Cost per mile	11.21p per mile
Cost of filling tank	£94
Monthly fuel cost
Annual fuel cost
NOx level	Extremely Low (trace)
CO level	Low
CO2 at tailpipe/tank-to-wheel (TTW) (g/km)	121
Official Euro emission level	Euro 6b
Engine test date	07 April 2015
Test programme	2012-2016

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Mercedes-BenzS-class Hybrid (2014-2018)

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