Why lube Oil turn cloudy/milky after 3 months of storage(indoor)? It's stored in the racks (clean and dry). How water content get into the oil? It's fully seal.

If ambient temeperature have big changes during the day -high temp during day time, low temp during nite - then:
1. drums are breathing, that means air can go in bringing humidity
2. water condensation coul be in process
Storage the drums upside down, doing this you will cerate an oil seal and avoid the air entry due to temperature changes.

Luis hit the nail on the head. EC appear to be from Singapore - hot AND humid climate.

- The drums can also be stored horizontally with the caps on 90 and 180 degrees preventing breathing.
- Assess the storage facility with regard to ventilation, the ambient temperature might be significantly amplified in a poorly ventilated enclosure.
- High humidity and heat have to be controlled therefore airflow is important.

a few things

1. Did you have the oil tested for water?
2. Were these un-openned drums from your suplier; if so, is the problem from your oil supplier?
3. Is it all of your oil types; motor hydraulic or gear oil
4. If it is only happening to open drums; Do you have desiccant air breathers on the drums?
5. In Singapore; I would be surprised if it was condensation. (heating - cooling cycles)
Consider install small lube storage tanks, use desiccant air breathers, water absorbtion dispensing filters and have the oil tested before use.

Could it be cause by improper blending?

EC may be on to something. If moisture is not the culprit, then the cloudiness can occur in cases where there is a high load of additives in oil, inability of base oil to keep additives dispersed without agitation, and/or high wax content present in the base oil. Also, ambient temperature, if low, could promote cloudiness. However, all this may not mean that the oil is of a lower quality. Simple agitation (using a food blender) of a sample taken from drums could be enough to give some answers. In most cases oil cloudiness disappears after oil has been agitated. An example is motor oil.

John