Sterling and Lutterus were joined at 11-under-par 205 by Peter Senior, who had a 3-under 69. They hold a one-shot lead heading into the final round at Kooyonga Golf Club.
Among the leaders, Lutterus and Senior are both native Australians. But Lutterus is the local favorite, a Kooyonga member who fired a 64 Thursday for the first-round lead but stumbled to a 75 on Friday.
Things turned for the better Saturday, when Lutterus had six birdies, two bogeys and an eagle at the par-4 sixth.
'Mentally I still believed I could play well today,' said Lutterus, 21. 'I knew how I played on Thursday and thought I was capable of that again and today I went out there with the same mind set.'
Senior also had an eagle in his third round, at the par-5 ninth. He added three birdies and two bogeys for his 69 -- this after shooting 68 in the first two rounds.
'I was happy with the way I struck the ball so I'm looking forward to going out for tomorrow's round,' Senior said.
Sterling was more consistent Saturday, posting seven birdies with just one bogey. His first birdie came on a 30-foot putt at the par-5 second, one hole before his only bogey.
'I pretty much made everything I was supposed to, plus three or four long ones,' the American described his putting. 'Just luck I guess, because you can't expect to make those.'
Fellow American Brad Ott shot his second-consecutive 70 and is alone in fourth place at 10-under 206. Ott collected three birdies, but missed his chance of sharing the overnight lead after making his only bogey at the 14th.
Chris Nallen (68), Brendan Jones (68) Gabriel Hjertstedt (69) and Greg Chalmers (71) share fifth place at 9-under 207.
Overnight co-leaders Brett Rumford and Craig Parry both had 1-over 73s and stumbled into a tie for ninth place at 8 under.