One of five native South Africans in the top 10, Schwartzel stands at 8-under-par 136 for his second career 36-hole lead on the European Tour. Late bogeys on both sides of his scorecard cost him a bigger advantage.
'The start was pretty good. I played well and I thought I'd be in for a nice low score,' said Schwartzel, the 2005 champion and a runner-up last year. 'But at the end I finished badly, but 68 is no disgrace,'
The top 10 players on the leaderboard are comprised entirely of players from South Africa, Spain and England.
Spain's Rafael Cabrera Bello (69) and England's Oliver Wilson (70) are tied for second place at 6-under 138. Englishman Lee Westwood (66) is alone in fourth at 5-under 139.
Titch Moore had the round of the day with an 8-under 64 and shares fifth place with fellow South Africans Hennie Otto (69), Wayne De Haas (72), Ian Hutchings (70), England's Phillip Archer (72) and Spain's Alvaro Quiros (66) at 4-under 140.
They are all looking up at Schwartzel.
Locked in a five-way tie for the lead overnight, and beginning his second round on Leopard Creek's back nine, Schwartzel distanced himself Friday with birdies on four of his first six holes.
He bogeyed the par-5 18th to make the turn at 7 under, then got as low as 10 under with birdies at Nos. 1, 2 and 4. Bogeys at two of his last three holes dropped him to minus-8.
Ernie Els, the defending champion and a native South African, got to 3 under with three birdies over his first five holes, then double-bogeyed the eighth and bogeyed the ninth.
Els had three more bogeys at 10, 11 and 13 -- dropping to 3-over and flirting with the cut line. But he recovered with a birdie at the 15th and a closing eagle at the 18th.
A four-time Dunhill winner, Els had his second 72 and finished the round tied for 34th at even-par.
Seventy-two players made the cut, which fell at 2 over par. Among those who missed the weekend were 1994 Dunhill champion David Frost and 2005 U.S. Amateur champion Edoardo Molinari.