Abstract: A cannister type diesel fuel heater that readily bolts on to a conventional diesel tractor comprising a closed container having two separate heat exchanger coil systems within the closed cannister. One coil is adapted to circulate diesel fuel coming from the fuel tank before combustion and the other coil is adapted to circulate excess diesel fuel returning to the fuel tank. By circulating hot crankcase oil from the diesel engine within the cannister in contact with the heat exchanger coils, the diesel fuel is heated before combustion as well as being heated upon return to the fuel tank. Such a system is particularly useful in maintaining the fuel system free of paraffinic deposits as well as improving overall efficiency and fuel mileage.