Careful cleaning is needed for cornhead grease.
"Polyurea grease compatibility is highly unpredictable because polyurea thickener chemistries vary widely. While some polyurea greases mix perfectly fine with lithium or calcium greases, many are completely incompatible. Mixing incompatible greases causes the thickener to collapse, resulting in severe oil bleed, hardening, or liquefying, which often leads to bearing failure."
https://www.machinerylubrication.com...-compatibility