Hello. As far as i know in general:low speed bearing are lubricated with high viscosity oil while higher speed bearing are lubricated with lower viscosity oil. The issue that i don't understand is: what is,exactly,determine that the bearing is high speed,medium speed or low speed.? the RPM of the bearing or the FPM of the bearing. For example,there are two rolling bearingne has small diameter while the other has much bigger diameter and them both have the same FPM.The small one will,obviously,have much higher rpm than the bigger one that could have relative much less rpm. So,do i apply the same viscosity of grease(oil) to them both,since them both has the same FPM? or the small bearing which has high rpm should be applied with different viscosity(lower)oil than the other ,inspite the fact that they are moving in the same speed(but different rpm)? Thanks in advance.