AN effort to bracket and clarify the controversial and widely encountered problem of varnish in engines, is the purpose of this symposium, Mr. Kishline announces. This he does largely by presenting and interpreting the experience, opinions, and questions of many anonymous SAE members and their companies on this subject. These contributions, he explains, were received from a large number of representative sources, and present a typical cross-section of this phase of lubrication.
Mr. Kishline defines the offending “varnish” as a “synthetic resinous compound” precipitated by little known chemical reactions, oxidation, exposure of oil to relatively high temperatures, presence of foreign materials, or various combinations of these causes. Varnish has been blamed for a long list of engine troubles, he explains, among them sticking valves and rings, engine surges, blowby, and seizure.
Under the heading, “What To Do About It,” the author concludes that varnish evidently is not partial to any particular engine design nor to any of the various combinations of design features that might seem logically to have some influence on the condition. It would appear that time and temperature are principal items in an engine which govern the condition, he says, and the temperature may or may not be the sump temperature. Possibly there is a critical temperature above or below which the formation is slight, he suggests, although one of the experiences contributed indicated varnish formation at temperatures up to 400 F.