thank u....actually I am looking for psu....

Yes this predictor will help you for PSU as well.

how do I prepare for ongc interview?? any guidance?

Some things to consider are:
Be honest and do not try to impress them, so not act overly.
Dress well.
Be prepared on answers like:
Why do you want to join this organisation?
Why do you want to leave your current company?
For each gap you should have a proper justification?
What are your strengths and weaknesses?
What do you see yourself after 5 years?

All the best.