How car makers fix official fuel economy tests

Official fuel economy tests on new cars are being fixed by car makers using a number of legal ‘tricks’ that artificially boost economy ratings. Has anyone ever bought a new car and ending up getting the sort of economy the maker claimed? Probably not.

In fact, we usually find car makers’ figures are out by anything up to a third when we have a car in for review, and they are really good for nothing except vague comparison between different cars.

Now it seems that it’s not just the fact that economy testing isn’t done in the real world that makes the figures so wrong, but that car makers are going to extreme lengths to ‘improve’ their figures and give them an edge.

A report from the Transport & Environmental Campaign Group claims car makers are overstating economy by at least 25 per cent and in some cases as much as 50 per cent (interestingly, the SMMT reported only yesterday that new cars are now 25 per cent more economical than cars from a decade ago).

Manufacturers are using a variety of tricks to improve their figures, including taping up panel gaps for improved air flow, using super slippery lubricants, disconnecting the alternator, changing wheel alignment and pulling brake pads off the discs, over-inflating tyres and testing at high temperatures.

Astonishingly, the system is so lax that all these ‘tricks’ are completely legal, so it’s no wonder official figures seem completely false.

We’ve long called for official economy testing to be done in the real world by a completely independent body, and the report from T&E shows how necessary this is. And at the same time we should be testing not for CO2 (although that’s just an extrapolation from the official mpg anyway) but for NOx and particulates instead.

It really is time to make the official economy tests useful.

By Cars UK