═════════════════════╤════════╤════════╤════════ ITEM │Fuel Oil│Kerosene│Gasoline │ 3c │ 6½c │ 15c ─────────────────────┼────────┼────────┼──────── 60 Gallons Fuel │ $1.80│ $3.90│ $ 9.00 Lubricants │ .40│ .40│ .40 Engineer │ 3.50│ 3.50│ 3.50 Plowman │ 2.00│ 2.00│ 2.00 Repairs │ .12│ .12│ .12 Cost to Plow 24 Acres│ 7.82│ 9.92│ 15.02 Cost per Acre │ .32│ .41│ .63 ─────────────────────┴────────┴────────┴──────── Plowing at the rate of 20 acres per day, and kerosene at 6⅔ cents per gallon, the Rumely Company obtain the cost of plowing one acre as $0.66. In the latter figure the interest and depreciation are included which will increase the figures over those given by Fairbanks Morse. It should be understood that these costs are approximate and will vary considerably in different localities and under various conditions. Oil Injection Engines. Engines using low grade fuels such as kerosene, usually experience much trouble in obtaining a proper mixture when the fuel is vaporized in an external carbureter even when the carbureter is specially designed for the heavy oil. This leads to fuel waste, starting troubles and cylinder carbonization, to say nothing of the objections of an odorous, dirty exhaust. To overcome the objections of carbureting the heavy oils it has been common practice to inject or aspirate a small amount of water, the water vapor tending to prevent the fuel from cracking and to distribute the temperature more uniformly through the stroke. The injection of water is not a particularly desirable feature, since its use involves one more adjustment and possible source of trouble when running on variable loads. In the semi-Diesel engine the fuel is sprayed directly into the combustion chamber by mechanical means, thus making the fuel supply to a certain extent independent of atmospheric and temperature conditions. After the injection the spray is vaporized both by the hot walls of the combustion chamber and the heat of compression, the latter being principally instrumental in causing the ignition of the gas. In this case no electrical ignition devices are required, thus at one stroke overcoming one of the principal objections to a gas engine.