The fuel consumption figures advertised by car manufacturers are calculated via the so-called Worldwide Harmonised Light Vehicle Test Procedure (WLTP) and include consideration of the given model's electric driving range. 'This would ensure manufacturers advertise more accurate figures and consumers have a better understanding of how much they should expect to spend on fuel.' 'It is clear that the standard set for calculating fuel consumption is flawed and should be reviewed to better reflect real-life driving conditions. 'Yet our research shows many hybrid models are not as efficient as the manufacturers claim, which means motorists could be spending more on fuel than they anticipated.
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'A fuel-efficient plug-in hybrid vehicle is an attractive feature for prospective buyers, as many will expect to spend less on fuel and reduce their carbon footprint,' said Which? head of home products and services, Natalie Hitchins. Which? said that their tests were tougher than the official ones, because they better represented real-world driving conditions.Ī recent report from Greenpeace and Transport & Environment called hybrid cars a ' wolf in sheep's clothing', as they emit 2.5 times the CO2 in reality than in tests. Meanwhile the Toyota Prius, the 'best' of the rest, was still 39 per cent below its official fuel economy rating and could cost up to £171 more to run each year. The worst offender, the BMW X5, was 72 per cent less efficient than claimed, and could cost its owner up to £669 more each year in fuel expenses. On average, hybrid cars were found to be 61 per cent less fuel-efficient than promised. The consumer watchdog tested 22 popular hybrid models over 62 miles (100km) and found that they had all been advertised with unrealistic fuel efficiency figures. Plug-in hybrid electric cars can use four times more fuel than makers claim, costing owners an average of £462 per year more than expected, Which? has warned.