BMW is about to become the first manufacturer to re-engineer a car to avoid the controversial proposed £25-a-day London congestion charge.

Carl Sanderson, general manager, product and market planning at BMW GB, said the move to lower CO2 emissions on the X5 diesel had been agreed at BMW in Munich in response to a plea from the British subsidiary.

The swingeing new higher rate of congestion charge, due to be introduced in October 2008, will affect all cars with a CO2 output of 225g/km or more.

Currently that includes the X5. The X5 3.0d – accounting for around 90% of the car’s UK sales – has a CO2 figure of 231g/km.

But diesel X5s produced from October, and on sale from November, will duck under the new higher-rate charge with a CO2 level dropped to 214g/km.

London Mayor Ken Livingstone’s plans for a £25-a-day congestion charge, as a pay-more-to-pollute-more measure, caused concern at BMW GB that it would lead to a dip in sales of the X5.

So a request was made to BMW in Munich to consider whether the car’s CO2 could be lowered to let the X5 stay within the £8-a-day category, Mr Sanderson said.

The key measures that will put the X5 3.0d under the 225g/km barrier include the introduction of brake energy regeneration.

It will also use flaps which can cut off the airflow into the front of the car when the engine is not at full load to improve aerodynamic efficiency. The changes are included under the firm’s fuel-saving EfficientDynamics banner.

Mr Sanderson added: “These changes add to the cost of the car, but they’re worth doing because of what’s happening to the congestion charge. For us this is like ring-fencing that bit of business we might lose with X5 customers in London.”