Why Grease Dries Up?

"What Causes Grease to Dry Out?"  

Contamination: Dirt, fly ash, etc. Incompatible grease.

Volatization: High temperatures. Low flash point. Cracking.

Bleed: Centrifugation. High temperatures. Incompatible grease. Low grease quality. Vibration. Low base-oil viscosity.

Oxidation: Heat. Water. Wear metals. Low-quality grease. Gamma radiation.