The company made the move to an ECO scheme three years ago, but found that it was not generating the expected savings.
Provecta claims the changes it has implemented mean Morgan Ashurst can now expect savings of more than £1,000 per car over the term of the contract, which currently involves 350 cars.
One of the main changes was the tailoring of car allowances for each driver, calculated on his or her individual total annual mileage.
John Homer, managing director for Morgan Ashurst, explained: “Previously all our drivers were under the same fixed contract, regardless of their annual mileage profile.
“While this meant that it was right for some drivers, it actually cost us money for others.”
All existing ECO drivers have the option to switch to the Provecta scheme at the end of their current contract and other qualifying drivers, including those who chose not to enter the original ECO scheme, will be given the option of joining for the first time.
Drivers will be actively encouraged to select cars with lower CO2 emissions.
Morgan Ashurst is offering drivers an extra £20 per month in their allowance if they choose a vehicle with 10% lower CO2 emissions than the benchmark car their allowance is based on.
Drivers also have the option of downsizing their vehicles and of keeping the cash they save.