Extended drain intervals for crankcase lubricants

The various approaches to achieving extended drain intervals in vehicle crankcase lubricants are described, with particular emphasis on commercial diesel engines. The various lubricant contaminants include soot, water, acids and particulate metals. Lubricant life may be prolonged by suitable design of the lubricant and of the engine, but more particularly by reducing the levels of contaminant in the lubricant such that the performance of the lubricant may be maintained. At the same time, wear rates within the engine must be within acceptable levels. The various options for reducing the levels of contaminant include lubricant by-pass filtration systems, including barrier filters, refiners and centrifugal filters.