When you look at a new or used car, one big factor that helps you make the right selection is fuel economy.  If you travel a lot, this is crucial. Even if you don’t, you still want the best possible fuel economy for your usage. However, experts claim that the difference between official fuel economy figures and those from real world use could be as much as 42% – with the real-world figures being the higher of the two.

The changing face of fuel economy

According to the International Council of Clean Transportation (ICCT), there is a massive 42% difference between the official fuel economy figures that are given out by car manufacturers and the results from real-world tests. This is a huge leap from 2001, when the difference between the two sets of figures stood at just 9%.

This misinformation could be costing drivers an average of £350 a year in extra fuel bills, the report revealed.

Fuel Economy

(Credit – Robert Couse-Baker)

Economy and emissions

The latest analysis is based on the official figures and also those achieved during controlled laboratory tests by the ICCT. It measured both CO2 emissions and the miles per gallon fuel efficiency. According to official figures, the CO2 output for new cars has been in gradual decline since 2008. However, the real-world tests from the ICCT painted a very different picture – the figures have changed little in the last five years.

This contrasts starkly with the information provided by car manufacturers. Official tests since 2012 show that the new car outputs of carbon dioxide have dropped by nearly 11%, to a new, lower average of around 120g/km. However, the real-world tests show that in the same period, the reality is a drop of only around 2% meaning cars hover at an average of 170g/km, polluting the atmosphere much more than drivers are led to believe.

The effect on fuel

Even if the effect on the environment isn’t at the forefront of drivers’ minds, the effect on fuel consumption and the resulting increased cost of running the car certainly will be. Higher emissions mean that cars use more fuel. The difference of 42% between official and real-world figures could be hitting drivers in the pocket to the tune of around £350 a year in extra petrol or diesel.

The news will no doubt particularly irritate diesel drivers, who are currently being scapegoated as the cause of all pollution around Britain’s towns and cities. With their vehicles classed suddenly as ‘dirty,’ after years of government advice to switch to this fuel type over petrol, as it is less polluting, many diesel drivers feel betrayed by the government’s change of direction.

Abject failure

According to Greg Archer of Clean Vehicles at Transport & Environment, the tests show the abject failures of the current CO2 regulations. The regulations were agreed in 2009. Since then, just 40% of the promised improvement has been delivered, with little real-world change to emissions for the last five years.

In addition to the new figures from the ICCT, the new WLTP test cycle is being introduced from September.  This is part of EU measures to have stricter new CO2 targets by 2030. The test isn’t mandatory until September 2018 but should produce more realistic figures. It replaces a test – the NEDC – which itself hasn’t been updated since 1997.

Performance gap

The ICCT says that while the new test will help the problem, more needs to be done to address the vast discrepancy between the official and real-world figures. It is also concerned that the new test could have ‘loopholes’ that could permit the performance gap to increase once again.

The European Commission has just released new targets for the next ten years, by which time 30% of all new vehicles should be electric powered. It also looks for the average CO2 output for vehicles to fall by 15% between 2021 and 2025 and by 30% by 2030. However, unless more accurate figures are achieved, it will be almost impossible to know if these standards are being met.

Are you surprised by the difference between official figures and the real-world data? Does your vehicle achieve the fuel economy that it should? Leave a comment to let us know. 

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