Wilson was at 4-under 212 heading into the final round, with halfway leader James Kingston in second place. Garth Mulroy was two shots back after a 64, the day's best round.
Greg Norman, recently engaged to tennis great Chris Evert, shot a 72 and was at 217. Defending champion Ernie Els, playing in his home country, had a 77 that left him way back at 224.
Wilson said the Jack Nicklaus-designed layout at Pearl Valley Golf Estates posed plenty of obstacles.
'On this course you have to just let it come to you,' the South African said. 'It's a different level of concentration where you're not trying to force anything, but rather just hit one shot at a time. There are a couple of holes where you feel like you can make birdie, but even if you make par you're quite happy. There's a lot of trouble out there.'
Els equaled his opening-round 77 after putting himself back in contention Friday with a 70. Els had three bogeys and a double bogey on the back nine.
U.S. Open champion Angel Cabrera remained at 9 over with his 72. First-round leader Robert Rock (71) was four shots behind Wilson.