Sportsman 500 HO Model Year Revisions
#32
The first number the viscosity for cold starts,the lower the number being better and quicker oil flow in cold, the second number is the viscosity once the motor is up to operational temp after warm up.
So in cold a 0w-40 oil will flow quicker than a 5w-30 upon start up, once warmed up its acts as a 40 grade oil . The first number is more important than the second number in cold conditions with multi grade oil.
These explains it better. http://www.upmpg.com/tech_articles/motoroil_viscosity/
You want the oil getting to the cam as soon as possible on the Fuji 500 motor on start up,especially being a dry sump motor.
So in cold a 0w-40 oil will flow quicker than a 5w-30 upon start up, once warmed up its acts as a 40 grade oil . The first number is more important than the second number in cold conditions with multi grade oil.
These explains it better. http://www.upmpg.com/tech_articles/motoroil_viscosity/
When you see a W on a viscosity rating it means that this oil viscosity has been tested at a Colder temperature. The numbers without the W are all tested at 210° F or 100° C which is considered an approximation of engine operating temperature. In other words, a SAE 30 motor oil is the same viscosity as a 10w-30 or 5W-30 at 210° (100° C). The difference is when the viscosity is tested at a much colder temperature. For example, a 5W-30 motor oil performs like a SAE 5 motor oil would perform at the cold temperature specified, but still has the SAE 30 viscosity at 210° F (100° C) which is engine operating temperature. This allows the engine to get quick oil flow when it is started cold verses dry running until lubricant either warms up sufficiently or is finally forced through the engine oil system. The advantages of a low W viscosity number is obvious. The quicker the oil flows cold, the less dry running. Less dry running means much less engine wear.
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