<P> Another manipulated property of motor oil is its total base number (TBN), which is a measurement of the reserve alkalinity of an oil, meaning its ability to neutralize acids . The resulting quantity is determined as mg KOH / (gram of lubricant). Analogously, total acid number (TAN) is the measure of a lubricant's acidity . Other tests include zinc, phosphorus, or sulfur content, and testing for excessive foaming . </P> <P> The Noack volatility test (ASTM D - 5800) determines the physical evaporation loss of lubricants in high temperature service . A maximum of 14% evaporation loss is allowable to meet API SL and ILSAC GF - 3 specifications . Some automotive OEM oil specifications require lower than 10% . </P> <P> The Society of Automotive Engineers (SAE) has established a numerical code system for grading motor oils according to their viscosity characteristics . The original viscosity grades were all mono - grades, e.g. a typical engine oil was a SAE 30 . This is because as all oils thin when heated, so to get the right film thickness at operating temperatures oil manufacturers needed to start with a thick oil . This meant that in cold weather it would be difficult to start the engine as the oil was too thick to crank . However, oil additive technology was introduced that allowed oils to thin more slowly (i.e. to retain a higher viscosity index); this allowed selection of a thinner oil to start with, e.g. "SAE 15W - 30", a product that acts like an SAE 15 at cold temperatures (15W for winter) and like an SAE 30 at 100 ° C . </P> <P> Therefore, there is one set which measures cold temperature performance (0W, 5W, 10W, 15W and 20W). The second set of measurements is for high temperature performance (8, 12, 16, 20, 30, 40, 50). The document SAE J300 defines the viscometrics related to these grades . </P>

What is the meaning of 10w30 engine oil
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