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Plug-in hybrids are using more fuel per gallon than originally advertised according to statistics

Peter Kelly
Feb 7, 2020

Fuel consumption in plug-in hybrid vehicles (PHEVs) was far greater than had been advertised according to a new study by The Miles Consultancy.

In a series of studies, fuel management firm The Miles Consultancy audited how much fuel was being consumed from PHEVs by a number of car drivers versus the advertised fuel consumption. The difference is shocking. 

According to their statistics, in cars such as the Mitsubishi Outlander and Mercedes-Benz C-Class, the real fuel economy (in miles per gallon) was less than a third the advertised fuel economy. Meanwhile the average BMW plug-in hybrids and the Volkswagen plug-in hybrids also consumed three times more fuel than was advertised originally. 



Plug-in hybrid
electric vehicle(s)
Advertised Fuel Economy 
(in miles per gallon)
 Real Fuel Economy
(in miles per gallon)
Mitsubishi Outlander 148.5 41.0  
Mercedes-Benz C-Class  130  39.0   
BMW plug-in hybrids (average) 137.0 42.0  
Volkswagen plug-in hybrids (average) 163.0 52.0 

SOURCE: The Miles Consultancy

There are reasons for this however.


Hybrids contain an extra electric motor and battery so these vehicles tend to be heavier than solely petrol powered cars, which is one reason for the higher rates of consumption.

Moreover many plug-in hybrid cars are not being charged efficiently, therefore being run on their petrol system a lot of the time; this nullifies the point of the hybrid's system as the combustion engine is meant to be there as a back-up.

"However, there is a concern that plug-in hybrids are not being used as intended, achieving less than one-third of miles in electric mode, and risking higher emissions.

"By the end of the year, most new models of fully electric vehicle will be able to cover 150 miles on a single charge, and the need for plug-in hybrids will inevitably decline."

These stats follow an announcement by Prime Minister Boris Johnson who aims to stop the production of petrol, diesel and hybrid cars by 2035.


Speaking at the launch of COP26- the UN's climate change summit- at London's Science Museum the Prime Minister stated: "I hope we can as a planet and as a community of nations get to net zero as I say within a decade."

"We're going to do it by 2050, we're setting the pace. I hope everybody will come with us.

"And lets make this year the moment when we come together with the courage and the technological ambition to solve man-made climate change and choose a cleaner and greener future for our children and grandchildren."

This desire to reduce climate change has led to the Conservative leader putting forward a pledge to ban the production of petrol, diesel and hybrid cars by 2035.

Speaking to the Telegraph, The Miles Consultancy's managing director Paul Hollick stated: "There is a real risk that drivers are adopting plug-in hybrid electric vehicles for completely the right reasons, but unknowingly actually increasing their fuel bills. 

"On the evidence of our sample, one has to question whether some plug-in hybrid electric vehicles ever see a charging cable. In a lot of cases, we see plug-in hybrid electric vehicles never being charged, doing longer drives and this is not a good fit for a lot of car users.

Nick Molden, Emissions Analytics chief executive, told the Telegraph: "This is all very confusing for motorists. The problem is the official figures are very sensitive to assumptions about how plug-in hybrid electric vehicles are being charged and driven."


Responding to The Miles Consultancy's study, a Mitsubishi UK spokesperson explained to the Telegraph: "The Mitsubishi Outlander plug-in hybrid electric vehicle was originally tested for emissions and fuel economy in a fully charged state. 

"The additional performance that the energy stored in the battery provides naturally has a significant impact on its overall efficiency.

"We state in our promotional material that the official figures are only for comparison to similar vehicles and that they may not reflect real-life driving results."

A spokesperson for Kia stated that the proper method for using plug-in hybrids is explained to buyers who purchase such vehicles, highlighting the benefits of the dual-system.

"But Kia cannot ensure that owners will always follow that advice once the vehicle leaves the supplying dealership – that responsibility lies with the owner. Used correctly a plug-in hybrid electric vehicle will improve fuel economy and reduce tailpipe emissions."

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