According to Lubrication Fundamentals, solid particles trapped between the rolling elements and raceways are the most common causes of shortened bearing life.  In order to extend bearing life, it is essential to keep dirt away as much as possible and change lubricants before oxidation contributes to deposit buildup.  Oxidation-inhibited lubricants can significantly extend the length of time lubricants can be left in service.

Amsoil Synthetic Greases have a much higher tolerance to heat than petroleum based greases thereby reducing such factors as Oxidation. 

Amsoil