He crafted a bogey-free round in testing circumstances - there were swirling winds to contend with and a weather delay of an hour and 42 minutes - to find himself two shots off the lead of Swede Alex Noren, who shot a 67 to move to eight-under at the halfway stage of the tournament.
He shares that second spot with four other players, including countrymen George Coetzee and Jaco van Zyl, representing a strong local challenge for the title which hasn't been in South African hands since Trevor Immelman won the 2007 event.
The others on six-under were Paraguay's Fabrizio Zanotti, who carded the tournament's first-ever ace on the fourth, and England's Chris Wood.
“Whenever I had a good opportunity for birdie, I took it,” said Oosthuizen. “You have those days and hopefully I can just build on this. It's been a while since I've made a bogey-free round. I'll take a lot out of this round today.”
It was a quiet start for the 2010 Open champion, with two birdies in his first eight holes, but then he turned it on around the turn with three birdies in a row on nine, 10 and 11. Another on 17, and he had turned things around from a frustrating first round.
“It was a tough round yesterday,” he said. “Felt like I hit the ball really well but couldn't keep bogeys off my card. It was great to finish level after all that, and then sort of build on momentum going on to today.
“But it was quite tough with the wind. The wind was all over the place, and you have gusts coming now and then, and it makes it difficult. I hit the ball well. I enjoy playing in a little bit of breeze, and shaped the ball a bit more.”
He's on a course that he knows well and on which he's had success before. “I've won the Dimension Data Pro-Am here before,” he said. “I love this place. I love coming back here. It's great playing on a great golf course.
“There's a lot of holes where you think you kind of overpower it by just bombing a driver, but you know, I took the hard route today. I hit a few three-irons and a lot of five-woods off the tee just to give myself a mid-iron into the green.”
He's also sure that there is a better round out there. “It's out there, even with windy conditions, I still left a few out there today,” he said. “You just need to hit the fairways and give yourself any iron, really, to get to the green and hopefully you see the lines pretty good and make some putts.”
Noren will be a tough customer to chase down, with his three victories on The European Tour in the last four months.
“You gain more confidence in yourself and your ability with winning,” said the Swede, “but there's so many good players out here. I've got to put two great rounds in to beat the other guys. I'd rather be ahead than behind.”
Oosthuizen know what he has to do: “It's a good spot to be in,” he said. “Need to play good golf over the weekend.”
African News Agency (ANA)
Original source: Oosthuizen makes his move at Sun City