Question: Write a short note on: SAE ratings of lubricating oils.
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Mumbai University > Mechanical Engineering > Sem 5 > IC Engines

Marks: 5 M

Year: Dec 2014

mumbai university ic engines • 3.1k views
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modified 3.1 years ago  • written 3.1 years ago by gravatar for Juilee Juilee2.3k
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  • SAE (Society of Automotive Engineers) ratings classify lubricating oils according to their viscosity. The method assigns a number to an oil whose viscosity at a given temperature falls in a certain range.
  • In order to assign the numbers two temperatures are used as reference: one is -18°C (0°F) and 99°C (210°F).
  • Oils defined in terms of viscosity at -18°C, such as SAE 5W, 10W and 20W grades, provide starting in cold climates easy.
  • Oils defined in terms of viscosity at 99°C, such as SAE 20, 30, 40 and 50 grades, work satisfactorily in normal and hot climates.
  • These numbers merely classify the oils and are not indicators of the oil quality.
  • Some oils, called multi-grade oils, are developed to exhibit more than one viscosity at different temperatures. Eg. SAE 20W/50 oil has viscosity equal to SAE 20W at -18°C and viscosity equal to SAE 50W at 99°C.
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written 3.1 years ago by gravatar for Juilee Juilee2.3k
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