We use a zinc free hydraulic oil in my facility and in several of the systems we often find as we change filters that the oil has jelled. If this jell condition is severe the filters will clog prematurely. If the jelled substance is removed from the hyrdraulic system it will return to oil. The oil supplier has taken many samples and each time the results are inconclusive in that nothing chemically is out of balance.
Has anyone else seen this with zinc free products? I'm puzzled.

Hi Ledforph

We have used a similiar zinc free hydraulic oil with ashless additves in screw compressors and faced similiar problems .We had taken a lot of samples and on analysis we found that the organic and inorganic acidity were present in most cases . This is due to the additves that are being used (phosphate esters) which normaly gets converted to phosphoric acid which reacts with the oil and causes jell like formation.

Please check with your oil supplier for the same.

dear ledforph
let me know what,s the color of jelly substance and what is the oem recomendation for lubricant and what is the operating temp.