Fuel Premium users have further permissions.
As well as being able to give users permission/access to the Fuel Product you can grant them different permissions for Fuel Allocation. This means some users can allocate for themselves only, and others can allocate fuel usage to assignees (fuel users) on the product.
Administer Fuel Allocations
Allocate Fuel Usage
Allocation Fuel Usage for Others
Learn how to change a users permissions here.