ASTM D4863 Standard Test Method for Determination of Lubricity of Two-Stroke-Cycle Gasoline Engine Lubricants
4. Summary of Test Method
4.1 The test has been developed to replace the CEC L-19-T-77 Lubricity Test, for which test engines are no longer available. It is run in a 49 cm3 single-cylinder air-cooled two-stroke-cycle engine operated at 4000 r/min wide open throttle (WOT) using a 150:1 mixture of gasoline and oil by volume. After conditions have stabilized, the cooling air is cut off. The output torque is measured when the spark plug gasket temperature reaches 200°C (392°F) and again when it reaches 350°C (662°F), at which point the cooling air is restored. The smaller the reduction in torque output during this period, the better the ability of the oil to lubricate the piston. This test is not normally damaging to the engine. Sets of five such tightenings are normally run, using alternately a benchmark reference oil and the non-reference oil for each set.
NOTE 1 - Pass-fail Criterion - The mean torque drop obtained with a candidate oil shall be the same or less than that with the reference oil as calculated by the procedures of Annex A4.
5. Significance and Use
5.1 The oil in a two-stroke-cycle gasoline engine is either mixed with the fuel prior to use or is metered into the fuel supply at, or at some point prior to, its passage into the engine crankcase. The possibility of the amount of oil actually present in the engine being less than optimum always exists. Also, with some oil metering systems short periods of operation with less oil than desirable can occur when the power is increased suddenly. It has also been found that the incidence of piston scuff early in the life of the engine may be related to the lubricity of the oil used as defined by test procedures of this type.
