According to new on-road tests by academics, the popularity of plug-in hybrid cars emits more carbon dioxide than official measures, adding to concerns over the real impact of cars sold as better for the environment.
According to the research by Switzerland s Graz University of Technology, the BMW 3 Series emits more than three times the advertised emission from cars from BMW, Renault and Peugeot.
Plug-in hybrid electric vehicles PHEVs combine a small battery with a traditional petrol or diesel engine. Carmakers say they can offer the best of both worlds by allowing owners to drive long distances while retaining the ability to drive with zero emissions. Campaigners argue that the cars are more polluting than claimed.
The research found that BMW's 3 Series emitted 112 g of carbon dioxide per kilometre, three times its official rating of 36 g. Peugeot's 308 polluted 20% more than its official rating of 27 g, while Renault's Megane was 70% above the official test of 30 g.
Independent independent groups, including the UK consumer group Which? PHEVs burn more fuel than the laboratory figures suggest. Burning fuel increases running costs and increases emissions of carbon.
The campaign group Transport Environment T&E commissioned the Graz researchers after similar analysis in 2020 found much higher emissions than advertised from PHEVs, particularly as some users don't charge them. PHEV technology in some newer models still pollutes more than official tests suggest, according to the latest data.
The BMW and the Peugeot didn't live up to their official zero emissions range. The Peugeot 308 managed just over half of the electric range, while the BMW 3 Series achieved three-quarters.
The tests showed governments should focus on incentivising the purchase of fully electric vehicles rather than hybrids, according to T&E. The findings come as the UK government considers which hybrids will be allowed for sale between 2030 and the complete ban on new hybrid sales in 2035. Some in the industry believe that a minimum zero emission range is required for cars to be allowed to be sold.
Anna Krajinska, vehicle emissions manager at T&E, said: Plug-in hybrids are sold as the perfect combination of a battery for all your local needs and an engine for long distances. In city tests, only one of the PHEVs has the advertised electric range, while all three emit more than claimed in commuter driving. PHEVs should be treated by lawmakers based on their actual emissions. Car emissions tests are carried out under rules known as the worldwide harmonised light vehicles test procedure WLTP, but critics say artificial lab conditions do not show the impact of driving in the real world. The Graz researchers instead used a portable test system and drove the cars around the city.
Carmakers argue that they have no choice but to include WLTP figures in advertising. If pollution reductions are overstated, lower pollution figures could lead to less stringent restrictions on PHEVs.
A BMW spokeswoman said: On-the-road driving presents infinite variability of multiple criteria and it is not surprising that there are some differences in the WLTP figures. BMW said that PHEVs play an important role in our transition to full electromobility as owners are more likely to move to battery vehicles in the future.
Renault has been approached for a response. Stellantis didn't want to say anything.