At the time of signing a deal, a single supplier may be able to provide the cheapest and best products, but in a dynamic market such as the fleet industry, that can change within weeks.
Regular benchmarking, either in-house of using an independent assessor, can ensure the right levels of service are maintained.
One firm the consultancy helped, which had outsourced fleet management to a third-party, found it received no discounts for daily rental business, despite a large annual spend on short-term vehicles.
Graham Rees, Fleet Logistics business development director, said: 'You cannot outsource financial responsibility, because that always lies in your business.
'But if you no longer own the process of managing your fleet, because it has been outsourced, how do you discover what is good, bad or indifferent about your service? Regular reviews are important.'
Fleet Logistics offers a service called FleetCARE, aimed at creating an independent 'layer' between businesses and suppliers, to ensure service levels and costs remain at benchmark levels, when operations have been outsourced.
Rees added: 'Using a single supplier often means that companies can lose commercial control of their fleet and often may not have access to the most favourable funding arrangements or purchasing/leasing deals. Solus supplier deals can be effective, as long as they are managed.'