Viezu Technologies showcased its fuel-saving devices at this year’s CV Show, promising savings of around 15%.

The firm remaps the fuel management systems in cars and vans, leading to lower CO2 emissions and better fuel economy. BT recently had 20,000 of its vans remapped and is seeing savings of between 12% and 15% – and is reckoned to be saving £3 million on its fuel bills.

Viezu general manager Alasdair Maclachan said: “Vehicle remapping offers fleets a host of opportunities and we’re being increasingly asked by companies like BT to help them achieve their own environmental and cost reduction targets.

“With an ISO certified process and a potential payback period of just three months, any technical risks are minimised and rewards can be felt almost instantaneously.”

But, we asked, would remappaing a vehicle's engine affect its warranty? Maclachan said: "We currently have 90,000 vehicles that have been remapped and we have a £5 million insurance policy against problems. If there is a problem we get an independent assessment to see whether or not the fault was ours. If it is then we fix it.

"However, in four and a half years we have not had a single problem."