Oram's dogged display rescued New Zealand from 45 for five to 327 all out in response to South Africa's first innings total of 276.
''Technically and just from a playing point of view it was probably my worst out of the three (centuries),'' Oram, who was playing his first test in 18 months after struggling with injuries, told reporters.
''I honestly did not feel very comfortable at all, I'm not sure if that was the pitch or just being away from the game and trying to get up to speed.
''But from the situation we were in at 45 for five it's probably my best, because I had to work hard and we got ourselves a very good lead.
''At the end of the day 133 is damn satisfying and I'm very happy to have contributed to our team.
''There are days where I feel a million dollars and it doesn't work for me, so I'm very happy to take this.'' Oram faced 169 balls and hit 18 fours and two sixes to give New Zealand a 51-run innings lead.
South African coach Mickey Arthur admitted his team had let the New Zealanders off the hook.
''We wanted a pressure-free day tomorrow, we wanted a nice lead but that was not to be,'' Arthur said.
''We didn't take the initiative after lunch and we let them get away.''