Fuel heating method and device for vehicles

In an internal combustion diesel engine including means for circulating an engine cooling liquid through said engine, and means for circulating an engine lubricating oil through said engine for lubricating the moving parts thereof, a fuel tank for said engine, and a device for heating diesel fuel circulating from said fuel tank to said engine, the improvement wherein said device comprises a heat exchanger, three separate heat exchange circuits within said heat exchanger, including a first circuit for circulating engine cooling liquid from said engine, a second circuit for circulating fuel from said fuel tank to said engine, and a third circuit for circulating motor lubricating oil, and wherein said heat exchanger includes means defining separate heat exchange surfaces between said oil circuit and said fuel circuit, between said cooling liquid circuit and said fuel circuit and between said oil circuit and said cooling liquid circuit, for effecting simultaneously direct heat exchange between the fuel to be heated and the motor lubricating oil, and between the fuel to be heated and the engine cooling liquid, such that said diesel fuel passing through said heat exchanger absorbs heat from the relatively cool engine cooling liquid and is further heated by the hotter motor lubricating oil to a significantly higher degree than that available solely from the engine cooling liquid without danger of overheating the diesel fuel.