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| Scientists discovered the use of polymers and the fact that these would expand with heat. VI Improvers are polymer material that expands as the oil warms up. This does NOT thicken the oil as is often stated. It merely slows down the rate at which oil thins out as the temperature rises. The base oil in use in a multi-grade (aka multi-seasonal) is the first number (such as 10W or 20W), where as the second grade is the viscosity achieved using the VI Improver (such as 40 or 50). 20W50 is a base oil of SAE 20W and the viscosity grade at running temperature is SAE 50.
http://www.kewengineering.co.uk/Auto_oils/oil_viscosity_explained.h...
This is a good explanation. | |
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Can someone explain oils to me please
