Mitsubishi cheats fuel economy testsMitsubishi confess to ‘improper conduct in fuel consumption testing’

20 April 2016

Mitsubishi tyres

Mitsubishi falsified tyre pressure information to get better mpg figures

Japanese car manufacturer Mitsubishi has admitted to falsifying test data on four cars in order to get a better mpg (miles per gallon) fuel economy figure.

Two thirds of people we surveyed in March this year listed fuel economy as one of the most important factors when buying a new car.

But today Mitsubishi has confessed it has ‘improperly presented’ information in order to state improved fuel economy rates for four of its cars. Mitsubishi achieved this by falsifying tyre pressure figures.

Over inflating tyres can be used to get better fuel economy in lab tests, but can be a dangerous thing to do in real life as it can reduce grip and increase braking distances.

However, inflating tyres beyond the recommended pressure is not against the rules in European fuel economy tests.

We’re campaigning for more realistic tests come in, as proposed, in 2017. Help us keep the pressure on for better, more effective tests by signing our Come Clean on Fuel Claims campaign.

Is this another Dieselgate?

No. Mitsubishi has manipulated mpg (fuel economy) figures, rather than emissions (pollutants) figures, as VW did.

Specifically, what Mitsubishi has done is to falsify tyre pressure information in order to get better mpg (miles per gallon) figures. The testing method used also differed from that required by Japanese law.

In contrast, VW Group manipulated confessed to manipulate NOx emissions, not fuel economy. NOx is a pollutant that is harmful to human health. All cars produce NOx, but diesel cars produce it in much greater quantities than petrol cars. We investigated emissions from all cars we’ve tested since 2012 and found some surprising information – check out our emissions investigation results.

mitsubishi eK Space

The Mitsubishi eK Space is one of the cars affected, and not available to buy in the UK

What cars are affected?

Mitsubishi has said four cars have false data: the Mitsubishi eK Wagon, Mitsubishi eK Space, the Nissan Dayz and the Nissan Dayz Roox. The two Nissan models are manufactured for Nissan by MMC (Mitsubishi Motors Corporation).

Sound unfamiliar? That’s because they are not available in the UK.

So why does this concern me?

Other than more general distrust of carmakers and their honesty around fuel claims, this does shine a light on a loophole in European testing: over-inflating tyres is not against the rules in our European tests.

This was brought to light by Mind the Gap, a report written by non-governmental organisation, Transport & Environment:

'Anyone who rides a bicycle will know that it goes farther and faster when the tyres have been pumped up hard. The same applies to cars, so a test vehicle will roll much farther when the tyres are pumped up as hard as possible. This practice is not specifically excluded in the test procedure, in spite of the fact that it would be dangerous to drive a car in this condition on a real road.'

Which means all manufacturers, including Mitsubishi, may be over inflating tyres in official mpg tests in order to get better fuel economy figures.

Richard Lloyd, Which? executive director said: 'People must be able to trust both car fuel efficiency and emissions claims, so after the VW scandal this news will raise more questions for consumers.'

So… has Mitsubishi (or anyone else) over-inflated tyres in European tests?

We have no evidence of this, but even if Mitsubishi was over inflating tyres here, it would not officially be considered cheating.

However, we have asked Mitsubishi if they have been inflating tyres beyond recommended tyre pressures and will publish its response when it comes in.

Can I over inflate my tyres for better fuel economy?

Over inflating tyres is dangerous. It can reduce how much of the tyre is in contact with the road which in turn reduces the amount of grip you have, increasing braking distances and cause uneven wear. Generally, it’s a bad idea and you should stick to the recommended tyre pressure.

More on this…