Unused lubricating grease can “go bad” if it is stored for an excessively long period of time, or under poor storage conditions. ... In addition, as oil tends to separate from grease over time, it can separate excessively if stored for a long time, to the point that the oil cannot be remixed into the grease.

How can you tell if grease is bad?

The surest way to determine that oil has degraded to the point of discard is when food begins to have an “off” odor or taste. This may manifest itself as a bitter taste, especially a bitter aftertaste. The food may also taste soapy.

Is it okay to use old grease?

You can use grease for up to six months when stored at room temperature, but it will be edible for additional few months if you put it in the fridge.