THE most striking improvements in lubricating oils for automotive-type Diesel engines have been obtained through the use of soap-type additives, the authors contend, and several brands of this compounded oil are now available to Diesel engine operators. The paper deals particularly with this type of addition agent and reviews the improvements obtained through its use.
Using such an oil, compounded with the calcium soap of dichlorostearate acid, the authors claim that five of the six properties considered necessary for a Diesel-engine crankcase oil are exhibited, namely-detergency which aids in preventing ring-sticking; high film strength which reduces the danger of scuffing, scratching, or galling under severe conditions; a high degree of oiliness which reduces wear under normal operating conditions; low carbon-forming tendency; and adequate crankcase stability which promotes cleanliness of the engine and maintains lubrication efficiency.
With regard to the sixth property-that the oil must be non-corrosive to engine bearings-the paper warns that all of the soap-type compounded oils now on the market are corrosive to the newer alloy-type bearings and, therefore, their use must be restricted to engines equipped with babbitt connecting-rod and main bearings. However, development of an all-purpose non-corrosive compounded oil is expected shortly.