With the information that the Sub is Russian made, I highly recommend that you take a sample and run it through an oil analysis. This will determine the type of product you need. I highly! Recommend you do this do to the sensitive application of the product. Unfortunately I cannot find an analysis lab in your vicinity. Perhaps you have one. I of course have contacts in North America. Here is the E Mail address for Noria Sub Saharan Africa
tdesousa@noria.com
Which is the closest I can find right now to you.
Good luck. Do not accept any "Could be's" or Might be's" you need the correct product for your application.