What should I do as Master if I found that C/E has made false entry in the oil record book ?

ORB is a legal document which requires to be signed by first C/E then Master. If you are aware of a false entry and you sign it then you are equally liable for prosecution. In such cases it is better to point this out to the C/E, cut out the entry clearly (cut entry should still be legible) and make correct entry. Sign the cut out entry and the final page at the bottom.

If C/E is not agreeing then don't sign it and bring it to the notice of your DPA or company.