The vehicle was driven in controlled conditions over a 49.1 mile course for the test at 0%, 25%, 50% and 75% of its 1,079kg maximum payload. The tests were all performed at the same time of day; an eco driving style was used and air conditioning was switched off.
Fuel consumption for an empty load was 35.74 mpg, rising to 33.79 mpg at 25% payload, 30.97 mpg at 50% and 28.16 mpg at 75% payload – an increase in fuel use of more than 21%.
“Fleet operators know that payload has an impact on fuel consumption, but perhaps are not aware of the degree. These results are marked,” says Liam Cresswell, Arval fleet consultant.
“A van that is carrying a 75% payload is using a fifth more fuel, which is a considerable cost increase.”
Cresswell says fleet managers must ensure vans carry only the loads needed and that drivers must be more aware of vehicle payload.
“It is also worth considering the question of storage systems,” he adds. “Good, modern, lightweight racking can help to maximise the carrying capacity and payload of a vehicle and generally increase its efficiency in use.
“Finally, this is an issue that can influence the selection of vehicles. A smaller vehicle operating near its payload capacity will always be a more cost-effective transport choice than an underutilised, larger van.”
He points out that even the unladen vehicle in the test was more than 25% adrift of the manufacturer’s official combined mpg figure.
“Official MPG figures are obviously carried out in controlled test conditions but this shows once again that they only provide an indication of performance in real-world conditions.”