<P> The engine would be started on gasoline and the tractor would then be worked until the engine was sufficiently warm to change over . At that point, the fuel valve would be turned to switch the fuel supply from the gasoline tank to the fuel tank and the heavy fuel would flow to the carburetor . Radiator shutters or curtains were typically used to keep the engine sufficiently hot for efficient operation . Coolant temperatures in the 200 degree F range were normal . John Deere two - cylinder all - fuel tractors worked well on heavy fuel, as their long piston strokes, slow engine speeds and low compression ratios allowed for efficient operation . Most were also equipped with thermosiphon cooling systems that used no water pumps . Natural convection allowed the water to flow up and out of the engine block and into the top of the radiator, where it cooled and dropped and fell to continue the cycle . </P> <P> Woody Guthrie's autobiographical novel Seeds of Man begins with Woody and his uncle Jeff tapping a natural gas pipeline for drip gas . The gas also has a mention in Badlands, the Terrence Malick movie . </P> <P> It was sold commercially at gas stations and hardware stores in North America until the early 1950s . The white gas sold today is a similar product but is produced at refineries with the benzene removed . </P> <P> In 1975, the New Mexico State Police's drip gas detail--three men in pickup trucks--began patrolling oil and gas fields, catching thieves and recovering barrels of stolen gas . The detail stopped its work in 1987 . </P>

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