Performance assessment of motor oils by the wetting angle

The problems associated with improving the reliability and durability of internal combustion engines largely depend on the quality of the fuel and lubricants used. One of the indicators of the quality of working engine oil is the wetting angle. It allows to assess the contamination of the oil with insoluble products and the ability of oils to disperse them. The method consists in determining the dispersing-stabilizing properties of a working engine oil, the degree of oil pollution by the contact angle of oil wetting on the surface of the substrate. Motor oil is a colloidal fluid that is layered. At the top of the drop is an additive that coagulates solid pollutants, at the bottom there is the base oil with a liquid pollutant. This method provides an unambiguous assessment of the dispersing and stabilizing properties of working oils, since the wetting angle in different layers of a drop of motor oil is taken into account. Contamination of engine oil with mechanical impurities, characterizing the dispersing properties of working engine oil, is determined by the angle in the upper layer of engine oil. Assessment of the wetting angle is to determine the boundaries of the spreading of motor oil on the surface of the substrate. Experimental studies have shown that: the wetting angle of a working motor oil on surfaces varies within: on a steel substrate from 5,36 to 20,62°; on a copper substrate from 7,45 to 20,39°; on a plain bearing substrate from 6,62 to 11,73 °. However, according to the results of the study, it was revealed that the substrate made of a plain bearing is wetted at any content of contaminants. From which it follows that substrates based on steel (cast iron) and copper should be taken as a criterion for the wetting angle, since they more closely reflect the diag-nostic feature.

wetting angle, coolant, antifreeze, engine fuel, substrate, oil film