The deal was worth approximately £14 million a year. The RAC fleet comprises 2,650 vans and 700 cars incorporating RAC Rescue and RAC Auto Windscreens.
Lex is supplying all vehicles on full maintenance contract hire with cars on three year/60,000 and vans on five years/120,000 mile agreements.
RAC has handed over all elements of running the fleet to Lex from ordering and supplying vehicles to all driver contact.
Debbie Hewitt, RAC managing director, said: "We chose Lex because of their absolute focus on the customer, the way they innovate in a very commoditised market and their commitment to continuously improve what they do for us.
“Everyone in the Lex team continues to demonstrate they truly understand our business and we believe this gives us the ideal combination of excellent service and very keen pricing. Their breadth of knowledge of this industry continues to bring significant benefit to RAC.”