1974-02-01

European Low Temperature Viscosity Requirements for Engine Oils, and Their Impact on SAE Classification Utilization 740975

CEC investigation group IGL-8 has conducted a survey of European engine cold starting and oil viscosity requirements. The group's objectives were to determine if the 20W bracket was too wide for European use and what alternatives existed for improving the matching of oil quality to manufacturer needs.A study of engine cranking speeds showed that the span of the 20W range is twice that of the 10W range for European cars. Car Cold Startability, and weather data analysis, also showed that the span covered by the 20W range was double that for the 10W range, and that a critical winter temperature for many more temperate countries was - 10°C (14°F). For many cars, an oil in the 48-64 poise range at - 18°C (0°F) would provide 95-97% confidence of starting in the coldest month-January-and would best match their needs. Some diesel starting data, particularly on small, high-speed engines appeared to show the same trends.Due to concern over high temperature operational problems, a number of European Car Manufacturers prefer mid-range 20W oils at the 45-64 poise level to 10W oils. Recognizing this, the CEC has suggested that the SAE may wish to consider establishment of an intermediate “15W” grade with 48 poise maximum at - 18°C (0°F). A minority also suggested reduction of the 20W upper limit to 64 poise, but this received only limited support because of worldwide impact on existing satisfied users of “high” 20W oils.

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