Too much water in the grease can cause corrosion and bearing damage. Cavitation can occur at points with high relative movement. If there is too much water or if water penetrates continuously, relubrication must be carried out more frequently. If a grease does not withstand the water, it may become soft or soupy and then washed out.

The amount of water in a grease sample is determined exactly in ppm (mg/kg) using the Karl Fischer method, as with oil. To do this, the water must be "expelled" from the sample. While in the case of an oil the water is evaporated from the sealed sample by heating up to 140 °C, this "boiling out" is much more difficult in the case of a grease. In this case, the water must be slowly dissolved out at 120 °C. The water is fed with nitrogen via a hollow needle into a titration vessel. Here it reacts electrochemically with a special Karl Fischer solution. The water content can be precisely specified via the inflection point of the titration curve.