LONDON – Commercial fleet operators in the U.K. could wind up suffering poor fuel economy by trading in diesel vehicles for hybrids.

That’s the warning from fleet software and management specialist FleetCheck, which claims a fuel-economy hit could be followed by worsened corporate emissions after switching to plug-in hybrids. It says a number of policy issues need to be tackled, from making charging points available to teaching drivers new on-road skills.

“With the ongoing demonization of diesel, plug-in hybrids are being presented as a potential like-for-like replacement offering similar fuel economy and improved emissions,” says Peter Golding, FleetCheck managing director.

“However, as some fleets are already finding, this is not really the case. Before committing to use this technology, organizations really need to ensure that they have policy measures in place to ensure that they access the benefits they seek. If they don’t look carefully at how they plan to operate these vehicles, they could find various problems arising very quickly, most notably poor fuel economy and the resulting increase in emissions.”

Golding emphasizes the importance of ensuring that drivers have access to charging, ideally both at home and at work.

“The strong fuel economy and emissions that plug-in hybrids deliver in the official figures are entirely dependent on their electric range being maximized,” he says. “If drivers cannot charge them easily, then fuel economy will suffer. Certainly, it must be a matter of policy that any driver issued with a plug-in hybrid should have off-road parking with charging available.”

Drivers also will need guidance on how to get the best fuel economy out of their hybrid, which might require changes in their driving style, Golding says.

“Depending on how the hybrid is engineered, some drivers will use the electric motor to add to the acceleration of the combustion engine and access very strong performance,” he says. “However, driving the car in this way will remove the fuel-economy advantages. Drivers must be shown how to get the most out of their hybrid, and this may require some kind of formalized training and regular monitoring of fuel consumption.”

In many cases, Golding says, fleets will conclude diesel still is the best option in terms of fuel economy and emissions. “For higher-mileage drivers especially, there is every suggestion that a Euro 6 diesel remains the most environmentally responsible solution, whatever the press, pressure groups and others are saying about its impact on air quality.”