Abstract: An overflow protection system for an oil tank trailer which automatically monitors and controls the level of oil within said trailer. The system comprises a float sensor, a cable assembly, a shutoff valve, a temperature sensor, and a control box. The float sensor comprises an inductive float sensor which monitors the level on the tank gauge of an existing trailer body, which provides electrical signals via the cable assembly. The cable assembly provides electronic connection between the float sensor, valve, temperature sensor, and control box. The shutoff valve is closed when the float sensor is triggered, preventing flow into and out of the tank in order to eliminate overflow spillage. The control box includes a plurality of manual user controls for operating the system as well as information displays including interior temperature and the like.