I don’t know abt the Lanka oil, but if it was me what I would do is get the engine oil flushed with a clean-up, filters changed and use Mobil XHP (if you’re already using semi-Syn). Run it for a 1k – 1.5k and get another oil changed with filters. AFAIK Mobil naturally got sludge dissolving capabilities. I would not really try something new though a foreman suggest. Number of changing oil will depend on your damage already done. Don’t think the issue has gone that for.
Anyway do the oil changes with lesser km’s on the clock than you used to do after a full cycle until you’re fully confident that the culprit is totally surrendered.