Gasolines and Engine Oils: Literature Review, New Laboratory Oxidation Method, and Significance of Olefins in Fuel

摘要

Review of literature on oxidation of gasolines and lubricating engine oils indicated shortcomings in present laboratory bench oxidation and engine tests. These tests are re-examined and their significance and some causes of poor precision are discussed. The newly developed laboratory oxidation method overcomes the shortcomings of the bench tests. The new method consists of oxidizing a liquid sample in an autoclave under oxygen pressure at desired temperature for a determined period of time. A uniform and constant reaction temperature is maintained by stirring both the sample and the heating oil bath. Gasolines rich in reactive olefins were found prone to oxidation. It is predicted that in the future gasolines may contain high percentage of olefins, gum precursors, because of their high blending octane number. Oxidative stability of formulated engine oil does not correlate with base stock oxidative stability or with the oil performance in engine and field tests. The lack of correlation is explained by the fact that the degradation of crankcase oil is caused by several factors, of which oxidation is only one.