A mobile CO2 filling system selectively fills onsite CO2 storage and dispensing systems with CO2. The system includes a mobile platform; a tank holding liquid CO2 mounted on the mobile platform; a flexible dispensing hose coupled to the tank and configured to be selectively coupled to the filling inlet of an onsite CO2 storage and dispensing system; A pump selectively coupled to the tank; and a controller for controlling the filling of an onsite CO2 storage and dispensing systems with CO2 from the tank, wherein the controller is selectively designated by the user to operate in at least one pump assisted filling state and at least one gravity feed filling state.