David Drysdale, who shot 67 Saturday, is alone in fourth at 14-under. James Elson (71 Saturday), Ben Evans (67) and Jean-Baptiste Gonnet (67) are tied for fifth, two strokes behind the leaders.
Schwartzel was 1-over after six holes in the third round before posting consecutive birdies on Nos. 7-9. He had another bogey at No. 15 -- only his third of the week -- before a birdie at the 18th hole moved him back into a tie for the lead.
Mulroy had five birdies and three bogeys in his round. He kept his share of the lead with a birdie at 18.
Aiken was alone in first after four birdies in his first 10 holes in the third round. He had a bogey at No. 16 that allowed Mulroy and Schwartzel to catch him with the finishing-hole birdies.