Here are a few examples of instrument rating oral questions:
Legality – Currency:
What specifically are additional aircraft equipment and inspection requirements for IFR fight?
Once an instrument rating is achieved, what are the legal ways to remain current and legal to file IFR?
Once an instrument rating is achieved, what are the recommend ways to remain current to file IFR (also include personal minimums)?
What are the different ways to perform a VOR check versus the different ways to perform a GPS check?
How much fuel is required for a IFR flight? How much for a IFR flight tower enroute?
How can I get airborne in IMC conditions in class G from a non-towered airport?
What specifically are additional weather briefing topics for a standard weather briefing for IFR flight?
What is the most common pre-departure topic/briefing that is either skipped altogether or performed only in insufficient detail?
The SID published and most likely assigned is not appropriate for you for performance reasons, what can you do?
Name different reasons why Tower en route obtained ad-hoc from the local clearance frequency may just be a really bad idea?
Other than minimum performance climb rates published in SIDS what are other minimum climb rates for enroute climbs?
Your destination is using a procedure turn but you are being vectored so the expectation is not to perform this procedure. Name reasons/cases why it would be very prudent to insist on flying the full procedure?