PSA Peugeot-Citroen is calling on rival manufacturers to follow its lead in publishing real-world fuel economy data after becoming the first major company to divulge its own data that is more representative of what drivers will achieve.

Although the current New European Driving Cycle test is due to be replaced in September 2017, PSA has moved ahead in releasing its own figures, and told BusinessCar that the biggest challenge is deciding how to successfully communicate these first results, published in July, when there isn't a consistent approach among other car makers for fleets to compare like-for-like.

"We're trying to encourage other manufacturers to use similar tests to our own and we're sharing what we do so they can repeat it in their own way," said Martin Gurney, PSA fleet director. "It looks like we are ploughing our own field here, but what we really want is a consistent approach so we can all be compared."

The European Union's Real Driving Emissions project forms the basis for the firms test, which has currently been completed on 30 vehicles across the Peugeot, Citroen and DS line-up. Conducted on around 60 miles of public roads made up of motorway, urban and rural routes, passengers and luggage are also taken into account and the air-conditioning turned on.

The tests found that on average the cars were 22mpg less efficient than the claimed figures suggest and Gurney admits that deciding what to do with these figures is a hard balance to get right; on the one hand, the firm wants to give the customers the real-world figures they are pushing for, while also maintaining the brand's positioning as Peugeot is currently ranked as the lowest-emitting manufacturer in Europe.