Abstract
The purpose of the article was to analyze the foaming tendency of engine oils used under excessive operating conditions. To achieve this end, foaming characteristics were determined for 23 oil samples in three measurement sequences. Foaming tendency was measured using the ASTM D 892 standard method, which consists in assessing foaming tendency of the liquid and foam stability. The cars used in the tests were uniform in terms of brand, type and operating conditions. The relationship between the mileage of the cars tested and the volume as well as stability of foam in used engine oils were presented using scatter plots with regression lines, correlation coefficient and 95% confidence interval. Based on the obtained results it was found that foaming tendency for new oils is characterized by high variability. The strongest foaming tendency at 24°C and 93°C (Sequence I and II) was observed for two out of five oil groups. Statistically significant differences were found between mileage and foaming tendency/foam stability for individual oils tested.
Highlights
Belonging to the group of operating fluids, engine oils are generally known to exhibit foaming tendencies. This particular property of oils may cause a number of unfavorable effects in actual use, such as: too low amount of lubricant applied to the brake assembly, increased compressibility of operating fluids, heat dissipation difficulties or accelerated oxidation
It is worth noting that unfavorable operating conditions and poorly structured oil circuits are conducive to foam formation
In sequence I, at the temperature of 24°C the strongest foaming tendency was observed in three samples from the MS oil group (MS 018011, MS 018361, MS 018128 with the following values – 680, 670, and 650 cm3, respectively) and in two oil samples from the ME group (ME 018345, ME 017973 with the values of 640 and 630 cm3)
Summary
Belonging to the group of operating fluids, engine oils are generally known to exhibit foaming tendencies. This particular property of oils may cause a number of unfavorable effects in actual use, such as: too low amount of lubricant applied to the brake assembly, increased compressibility of operating fluids (resulting from the presence of air bubbles), heat dissipation difficulties or accelerated oxidation. The foaming tendencies of engine oils represent a serious problem, especially when they are stronger than what might be deemed permissible under given operating conditions. Resistance of the operating fluids to foaming depends on many factors, including the chemical and physical properties of these fluids. It is worth noting that unfavorable operating conditions and poorly structured oil circuits are conducive to foam formation
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