20 Mar 2013

Why stated mpg figures don't reflect reality, and why we don't care

The BBC has reported on the various tricks used by car manufacturers to return better figures for mpg and CO2 than their cars can actually achieve.

Car manufacturers have to submit their vehicles for tests in order to measure emissions and economy figures.  In order to achieve the best results the manufacturers employ measures which produce better results than the car would ordinarily achieve on the road.
All these tricks are legal and fall within guidelines for the tests, which are set by the European Union.  It's just that, as happens in Formula 1, the manufacturers comply not necessarily in the 'spirit of the rules'.

Tricks include:
  • Pumping up tyres to reduce rolling resistance
  • Removing wing mirrors to reduce drag
  • Brakes are disconnected to reduce friction
  • Panels gaps are taped up to reduce drag
  • Disconnecting the alternator so there's no drag on the engine
  • Special oils are used to reduce friction in the engine
  • Turning off all and any electrical gadgets to reduce drag on the engine
You can read the full BBC report here.  The mpg and CO2 figures are used by regulators when setting emissions targets, by consumers looking at the economy level of particular cars, and by governments when setting tax levels.

And it's that final use - government's setting tax levels - which sticks in the craw.  The rules for testing cars' emissions levels are due to be changed in 2016 and you can bet that governments will use the new lower levels of mpg and higher levels of CO2 emissions (by making the tests more akin to real world conditions) to penalise motorists even more.

Motorists pay tax on purchase, tax on petrol, tax on the road fund licence, tax on garage bills, tax on company cars.  If it's got wheels and an engine governments will tax it.  We're easy meat.  We motorists pay for the rail users, the bus users, the roads and the rail tracks - and we pay for all that bureaucracy which works out how to make us pay even more tax.

When we're looking to buy a car we check the CO2 and mpg figures and treat them with a pinch of salt.  We know the figures are inflated.  We have common sense.

The only reason the government wants to tighten up the rules on emissions testing is to get us motorists to pay more tax, so they can waste it on bureaucracy and give it to other people.