Inclined or vertical shafts can lead to grease escaping from the bearing due to gravity. This will eventually lead to lubricant starvation and eventual premature failure of the bearing. Consider using a grease with good adhesive properties of penetration class 2 to 3. In addition, a baffle plate mounted in the housing below the bearing will help to retain the grease where it is needed - in the bearing. (Derek Peasley, FAG Bearing)

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Book Bits: Heat Means Trouble for Grease

From "The Lubricating Grease Guide"

Greases fail more rapidly as temperature of operation increases. The most obvious reason for failure lies in the melting point of the thickener or dropping point of the grease. The latter involves a complex process of melting and bleed. Evaporation may be significant at high temperatures. Oxidation also increases rapidly as temperature rises. There are useful guidelines for heat resistance of greases in service which take all these factors into consideration.

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QUESTION: What inspection needs to be performed when draining oil from a sump or reservoir?

Get the answer.

"My laboratory provides feedback on kinematic viscosity at 100°C for our engine lubes. At what level of viscosity change should we drain the engine oil?"

Because viscosity changes can indicate a number of problems whether the change is an increase or decrease (or both, therefore negating any perceivable change), monitoring viscosity alone as an indicator of engine oil change is insufficient, especially on engines.

Engines can suffer fuel dilution resulting in a decrease in viscosity, as well as glycol or soot loading resulting in an increase in viscosity. Changing the oil will not cure the root cause of these problems. In addition, if a multigrade engine oil is used, then a decrease in viscosity is possible because the viscosity index improvers shear in service. Further inspection or a more detailed confirmation analysis will be necessary to determine the cause if the viscosity has changed before the end of the anticipated service life.

However for engines, setting both upper and lower caution and critical limits will be an alert to oil life and contamination issues. The recommended lower limits are -5 percent and -10 percent, while the upper limits are +10 percent and +20 percent. These kinematic values are based on changes in cSt at 100°C.

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