A system for warming the engine of a water-cooled vehicle by exchanging coolant with a warm vehicle or a storage tank of warmed coolant. The system utilizes a fitting that, in one position, allows for normal function of the cooling system of a vehicle, and in another position the fitting allows for fluid exchange with an outside source, such as another vehicle. The outside source can be a second vehicle equipped with a fitting or a standalone heater. Fluid transfer hoses are connected to each fitting to exchange coolant between vehicles.