Going over what you didn't answer in EKM and EKG might be a good idea. Safety topics are quite important too, most deaths at sea are in confined spaces, so make sure you're covered for confined space entry. I was grilled (and I mean GRILLED!) on what to do in an engine room fire. ("That didn't work, NOW what do you do?" "Fire's getting bigger, where are your people?" "Hydrant's stuck, the 3rd hasn't checked it" "No grease on the vent flap hinges or butterfly nuts, WHAT DO YOU DO??") Keep in mind that heat damages wiring and electronic gizmos, so does water. Engine rooms have CO2 systems for a good reason!
SAFETY is Priority 1, especially as a 2nd Engineer, where you have the responsibility of your people as well as that of the Mechanical Gardens.
Did you have heat treatment of steel in your exams, hardening, tempering, annealing etc? You might get it in Orals.
Most importantly DO NOT BULLSHIT! The Examiner is a better bullshitter than you'll ever be, that's how he got to be an Examiner. If you don't know, say so, but don't play dumb, either. Orals give you a chance to correct any errors you made in the written papers. In EKG, I was asked to sketch and describe an instrument for measuring the density of brine and indicate the units on the scale. Well I sailed on reefers as 4th and 3rd for years, I knew all about a Twadle meter! Did a lovely sketch of it. When I got to Orals, (in Victoria) I was asked what happened when I added Calcium Chloride flakes to the brine. Did the meter go up or down? A horrifying realization hit me like a bucket of ice water, I had drawn the scale backwards! As soon as I said that, the Examiner smiled and said OK.
In Orals, as in the written exams, remember the K.I.S.S. principle. As this point, the last stage before the Certificate, it's more about what you've done than about what you've studied. The toughest Oral I ever did didn't contain one question. The Examiner just chatted about the job, (as Engineers are wont to do) talking "shop", discussing this and that, swapping experiences, telling sea stories. I didn't realise at the time (I thought he was being nice and putting me at ease), but I was being filleted! Bullshit may baffle brains, but don't think that in the Orals room, you're not in the same bullshit league!
Discourage incest, ban country "music".