Additionally, BT Group typically replaced its ‘volume’ fleet; vehicles - Ford and Vauxhall panels vans – at three or four-year intervals, but the data analysis revealed that vans could operate over more flexible periods.

As a result, many vans now operate over 54 or 60 month replacement cycles although some specialist vehicles, which have also been remapped, are operational for eight years.

Fielder says: “Vehicle life extension ultimately led us to consider ECU remapping. Engine remapping equals fuel savings, which equals cost reduction and the savings are considerable.”

ECU remapping across 23,000 vehicles – the remaining third of the fleet is not suitable due to a variety of factors including usage – has delivered average fuel efficiency gains of between 10-15%.

“The initiative has delivered substantial environmental gains: a 20% reduction in CO2 emitted – 25,000 tonnes –which is equivalent to 5,000 vehicles being removed from the fleet,” he says.

BT Fleet worked with Bromsgrove-based vehicle tuning and engine control unit remapping specialist Viezu Technologies to assess remapping viability and eventually individually remap each van according to operating parameters and payload instead of the generic setting from the factory.

The ECU is used to control a  variety of vehicle characteristics, including throttle, engine rpm, torque and speed, which in turn determines power output, mpg and CO2 emissions.

Some employees, he admits, were surprised at the improved driveability and better performance despite the focus of remapping being on fuel efficiency improvements.

Shaun Rowley, BT Fleet senior product marketing manager, says: “As we know the exact operating parameters of each van we are able to optimise ECU settings. In some cases that may mean improved driveability and better performance – increased engine power and torque – particularly lower down the rev range, but overall fuel and emissions savings are made.”

Remapping is typically undertaken as vans are serviced or MOT’d at BT Fleet’s own garages by technicians trained to undertake the work.

Viezu Technologies supply the bespoke remap file to a BT Fleet garage within five minutes.

Some BT Group vans have been remapped while the engine remains under manufacturer warranty.

Rowley says: “ECU remapping is not a product that will cause engine damage so all of our ‘volume fleet’ has gone through the programme irrespective of vehicle age.”