Early railroad motor cars and tractors were offered with kerosene or gasoline-powered engines. Beginning in 1925, distillate-powered versions were offered, persisting until 1956, when the last "all-fuel" tractors were sold, while diesel-fueled tractors increased in popularity. Kerosene-engined tractors were phased out by 1934. Distillate fuel was used in machines with specific provisions for distillate, as well as all-fuel tractors which could handle
kerosene,
gasoline or distillate. Tractors designed for distillate could operate on gasoline, and were usually started with gasoline, but since they operated at a much lower
compression ratio than gasoline-engined models, they developed less power on gasoline, and had to be warmed up with the more easily-volatilized gasoline before they could switch to distillate. Compression ratios for distillate could be about 4.7:1, while gasoline engines would run at 7:1 or more. Such machines were provided with small gasoline tanks for starting and warming up. However, distillate was often substantially less expensive than gasoline in farming regions, either because it was a less-refined product or because it was taxed at a lower rate or untaxed. "Power fuel" was a higher grade product that was somewhat short of gasoline in effectiveness. ==Distillate fuel oil==