DISCUSSION is given of the increase in severity of conditions for lubrication in the last few years, during which the engine designer has been calling upon the oil chemist for special oils to correct difficulties in operation. The 51% increase in horsepower in 10 years is proportioned between increase of compression ratio, intake system, displacement, and speed. Increase in severity of mechanical and thermal loading is due both to increase of rotative speed and brake mean effective pressure. Cooling done by the oil has been increased, and pistons are hotter than formerly. Crankcase temperatures have risen.
Compounded oils do not eliminate the basic rate of change of deterioration of oil with temperature. Compounding delays the start of deterioration and lowers the absolute rate.
Too many engineering problems recently have been left to the chemist to solve. Several cases of lubrication difficulty are discussed, and a method of analysis is described which shows accurately what any oiling system will do, and can locate most of the troubles. The general fault nowadays is too low an oil flow over the bearings for cooling and unnecessarily high crankcase temperatures.
Compounded oils are bound to incease in the future, but ultimately each must cover a much wider range of usefulness than any present single oil covers. A short discussion is given or means for increasing brake horsepower without increasing the octane demand of the engine.