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Crankcase lubricants for automotive and commercial use are differentiated by their physico‐chemical properties but more importantly by their performance in a series of engine test sequences. The sequences are devised by committees formed by representatives from the vehicle manufacturers, the oil companies and the additive suppliers. The article describes the sequences devised by the American Petroleum Institute and the European ACEA organisations, including some historical background as well as the current specifications. Methods of compliance monitoring and enforcement are also covered.

Manufacturing methods of white mineral oils are described, together with a summary of their major use areas. Recent toxicological studies using white mineral oils of various categories are covered. A summary of the current acceptable daily intake levels for such substances is included.

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.

Problems associated with inadequate fuel lubricity were identified in the aeronautical industry in the 1960s, following a succession of in‐flight engine failures. The influence of fuel composition upon fuel lubricity was established, as was the effect of various lubricity additives. Problems associated with inadequate fuel lubricity were also subsequently identified in light‐duty diesel engines when low‐sulphur fuel was introduced. Again, the use of additives or modifications to the refining process overcame the problem at the time, but the continuing trend towards higher injection pressures may require further improvements in current fuel lubricity. The manufacture and use of biodiesel is described, together with the attendant benefits, including use as a lubricity additive in conventional diesel fuel, also disadvantages. The imminent introduction of direct‐injection gasoline passenger car engines has now focused attention on the lubricity of gasoline, which is again likely to become a key issue. Two standardised test procedures for the measurement of fuel lubricities are described.