Nugen S10KS, Operator'S Maintenance Manual

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OPERATOR & MAINTENANCE MANUAL
PAGE ‐ 41
CLASSIFICATION OF ENGINE OIL
SAE (Society of Automotive Engineers) Standards are generally used to classify engine oil
viscosities. Viscosity is a principal property of oil, the higher the viscosity, the thicker the oil
film formed over the metal surface will be and the lower the viscosity, the thinner the film
thickness becomes.
Viscosity varies with temperature. The higher the temperature, the lower the viscosity and
vice versa. Engine oil should have the appropriate viscosity and have properties which are
not affected by viscosity changes caused by temperature changes. In other words, engine oil
must have a high viscosity index. Multi grade oils having relatively low viscosity (For example
SAE 10W ‐ 30) can provide superior lubrication at both low and high temperatures. Such oils
are available commercially for all ‐ season use.
Oil viscosity changes in cold temperature as crystallization of the wax element contained in
oil proceeds, and fluidity is finally lost. Incorrect selection of oil cannot only increase
resistance for cold starting but also affect lubrication of each part. Oils for low
temperature, containing additives for lowering the pour point, should be used. The following
diagram shows how to select lubricants.
Warning
Poor quality oil will shorten engine life. Use only the specified lubricating oils. Important
points regarding lubricating oil are described below.
Note
：
The use of synthetic oil is not recommended.