Overloaded vehicles such as those carrying bulky ladders, roof racks filled to the brim or even open windows could have a bearing on fuel consumption.
Studies from the Department for Transport have shown that open windows can create significant drag which can increase fuel consumption by as much as 7%.
Steve Crawshaw, LCV manager at LeasePlan, has urged fleet managers to ensure vehicles are as aerodynamic as possible.
He said: “The subject matter might seem more at home in a Formula One cockpit, but the principles apply equally to vehicles of all types. With vans often highly customised and regularly making long trips up and down the motorway, fuel efficiency can be a big issue.
“By making sure vehicles are as streamlined as possible and that drivers are playing their part in reducing drag, van fleets can knock thousands of pounds off their annual fuel bill.”