Oil will separate from grease for a number or reasons. It is important to point our that oil separation from grease is normal, it happens with most grease, both synthetic and mineral but of course the amount of oil separation will vary depending on the chemistry used in the grease, the storage conditions and other factors.
If oil separation is noticed, the oil can be mixed back into the grease to ensure the grease properties are returned back to their intended state. Oil separation is much less likely to occur in small packaging especially where the grease is contained on all sides (such as a tube or syringe), however jars are and exception.
Our partners at Nye Lubricants have created a YouTube video demonstrating how customers can safely mix oil back into grease. The video shows oil mixed back into grease when container in a 35LB pail (sometimes referred to as 40LB pail depending on the density of the grease).