Hi, we are using Shell Tellus 100 for a rotary bearing / friction device. After only several thousand revs at approx 20 rpm the performance of the device changes. We have noticed a brown, thin possibly sludgy deposit on the surfaces. This wipes off easlily. We believe this could well be affecting the performance due to a change in the frictional characteristics etc., Can anyone give an explanation as to what this could be ?

Pat.

It might be from the product itself if it ie. over-heats. Have you tested the oil? I recommend sending an oil sample to nearest lab and if possible a sample of the sludge. Check for low water content, TAN and other oxidation factors in the oil, and additves (like Phosphorus) in the sludge.

Is this oil original fill or it is a replacement. If it's a replacement, how extensive flushing was performed? When was last added make up oil, and how much? I am asking this, because of possible incompatibility between additives from old and new oil.