ADAPTING THE FUEL TO THE ENGINE ¹

Processing or refining costs for the different oils are difficult to estimate and of little significance in determining the selling price, which is controlled by the law of supply and demand. All types in the last list can be used in so-called heavy-oil engines, but the gas oil and light residuum are most desirable in the order given. They are less plentiful than the heavy-residuum type which generally cannot be used without special equipment for preheating. The proportionate yield of gas oil can be increased if a sufficient demand is developed. It is not yet settled whether on general principles it is desirable to design and construct engines that will utilize the heavy-residuum products or it is desirable to pay the additional price that will induce refiners to produce larger quantities of gas oil.