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High-temperature effects. High
temperatures harm greases more than they harm oils. Grease,
by its nature, cannot dissipate heat by convection like a
circulating oil. Consequently, without the ability to
transfer away heat, excessive temperatures result in
accelerated oxidation or even carbonization where grease
hardens or forms a crust. Effective grease lubrication
depends on the grease's consistency. High temperatures
induce softening and bleeding, causing grease to flow away
from needed areas. The mineral oil in grease can flash,
burn, or evaporate at temperatures above 177 EC (350°F).
High temperatures, above 73-79°C (165-175°F), can
dehydrate certain greases such as calcium soap grease and
cause structural breakdown. The higher evaporation and
dehydration rates at elevated temperatures require more
frequent grease replacement.
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