By the numbers
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Posting Guru
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By the numbers
What do the numbers mean on the oils that we talk about? what does the 5 and the 4 mean in 5w40. W=40 weight....but what really does that mean? Inquiring minds would like to know.. :-)
Post Fiend
Joined: Jul 2005
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From: 21791
lets start out by saying a 0 weight oil has the viscosity of pure water at room temperature.
viscosity is the resistance to flow.
the first number means that the oil will flow the equivalent of that when cold. the W after the first number doesnt mean "weight", rather it is "water" which i think means that it will have the resistance to flow that many times the viscosity of water. second number means the weight it will act like when the engine is at operating temperature. if you want me to go into detail, i can tell you why you want a multigrade oil, and also i can explain the API serivce ratings.
viscosity is the resistance to flow.
the first number means that the oil will flow the equivalent of that when cold. the W after the first number doesnt mean "weight", rather it is "water" which i think means that it will have the resistance to flow that many times the viscosity of water. second number means the weight it will act like when the engine is at operating temperature. if you want me to go into detail, i can tell you why you want a multigrade oil, and also i can explain the API serivce ratings.
