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OF the many characteristics of diesel fuels, heating value, ignition quality, and possibly fuel viscosity are the only important ones affecting engine power and economy, the authors disclose. In their paper they present data obtained from an extended fuel research program concerning the power and fuel economy obtained when using fuels differing in their physical and chemical characteristics. The points which seem to the authors to be of greatest practical significance are summarized as follows: 1. Assuming complete combustion, fuel volatility affects the pints per brake horsepower-hour only indirectly as it is related to heating value and ignition quality. 2. Most present-day engines have fixed injection timing and, on such engines, ignition quality is a major factor in determining volumetric fuel economy in the upper speed ranges. At the lower engine speeds, heating value in terms of Btu per gal, or as estimated from API gravity, is the most important consideration. 3.

STARTING, oil pumping, sludging and wear are the subjects considered specifically in connection with low operating temperatures. Tabular data and curves relating to starting are presented. Sludge is more dangerous in cold-weather operation, and the importance of selecting a quality non-sludging oil is emphasized. Tests to determine the causes of sludging are described, and the five conclusions reached are stated. The indications that wear is due to corrosion, rather than to removal of lubricant from cylinder walls, are analyzed. With regard to kerosene and Diesel engines, the author states that it seems reasonable to believe that the effect of operating temperatures, as such, with resultant moisture condensation, will result in at least equal relative wear to that which obtains in the gasoline engine. In conclusion, seven general rules are stated whereby the utmost satisfaction may be obtained during operation at low temperatures.