Major winner Oosthuizen produced a masterclass of mid-range putting and bunker play as his four-under-par 67 took him clear of Zambian Madalitso Muthiya, Matt Wallace of England and overnight leader Charl Schwartzel in the European Tour event.
Oosthuizen, who has not won a tournament in two years, picked up two shots in his first 10 holes and recorded three birdies on the back nine, despite windy conditions, to race ahead before dropping a shot at the 17th.
“It was tough with the windy conditions. I hit a few bad drives but the putter rolled nicely. I played solid, pretty good,” Oosthuizen said.
“I’ve been putting well for a long time now and today the makeable ones went in.”
Masters winner Schwartzel carded a third round 72 to drop off the top of the leaderboard but the potential of chasing his good friend offers hope of an exciting final round on Sunday.
The 35-year-old Muthiya, ranked 1,330th in the world and with career prize money of only 26,014 euros ($29,593.53), was level par for the day as he kept alive his hopes of a fairytale success while Wallace hit six birdies but suffered three bogeys on the back nine in carding a 68.
There are a further six players bunched on eight-under-par, including veteran Ernie Els who was 10-under before dropping shots in his final two holes.
The 49-year-old Els won the last of his five SA Open titles in 2010.
($1 = 0.8790 euros) (Reporting by Mark Gleeson; Editing by Ken Ferris)
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