Lock system preventing mixing of different kinds of oil at gasoline stand

A system for preventing filling any tank at a facility having a plurality of tanks containing different liquids with an improper liquid from a vehicle carrying a plurality of different liquids in separate compartments, at least two of the different liquids in the compartments of the vehicle being the same respectively as the different liquids in at least two of the tanks of the facility, said system comprising,

• a separate valve for each compartment of the vehicle, each valve being movable to an open position to permit flow of a selected liquid from a selected compartment of the vehicle,
• each tank of the facility having a separate filler port for filling a liquid into its tank, a lock on each filler port, a lock on each valve of the vehicle, a lock for the filler port of a tank at the facility being unlockable only by the same key which can unlock a valve of the vehicle for the compartment containing the same liquid, a plurality of keys, one for each filler port for different liquids, and one for each valve of the vehicle for different liquids, and key storing means at said facility for storing said keys, said key storing means comprising means to permit removing only one key at a time from the key storing means, so that only one key for one kind of liquid can be removed at a time, whereby, only the lock of a filler port and the lock of a valve for a corresponding liquid can be unlocked at the same time, so that inadvertently mixing improper liquids is avoided.