Diesel Engine Oil -Is it bad??

Just some suggestions. You may need to find out what coolant is being used and the additive package level - which may explain the high K. As for the phos, may need to check they are still using the same oil as before - possibly get a sample of the new oil to compare elementals and add pack levels. As for Ni - check if the engine has been overhauled or what works/repairs have been done - also find out what it's carting - is it a nickel ore of some sort. I hope this helps.

Agree with Rene, would also check fuel using ICP as there appears to be something strange occuring.
Also some rail engine oil is Zinc free(ZDDP free ZN~0 and P~0ppm) so the use of this may be the reason for phosphorus levels reducing.
Ni level puzzling, if Ni ore dust would expect increase in wear metals due to abrasive wear, too high for Fe/Ni alloy wear and no Fe.
Any Ni plating?
Suggest talk with engine builder

raveen - what breed of loco?

Ni is of concern, as you know it is used in a multitude of materials/comonents of EMD's, GE's alcos etc....

Potasium sounds like coolant - water can boil off and potassium can dgrade leading to fluctuations in results over time

Sulfur levels can be a function of changing fuel supplies (not familiar with asian rail fuel spec)

If you give me more details on your engine and its condition I can give you some suggestions on sources of wear elements and the parent assemblies it is liberated from

...also ask the boys if they use nickel antiseize on rod bolts etc....the concentrations of nickel in these types of products will not necessarily deplete with time

If its an emd 2 stroke loco engine find the model designation ie. 645e3b it will tell you if it is a cast iron or chrome bore etc whick will help you work out your wear element map for your fleet