Australia returned to the top of the world one-day rankings after surviving a dramatic late batting collapse to beat South Africa by two wickets at the SCG on Sunday.
The tense victory sealed a 4-1 series win for Australia as they build momentum to the World Cup which starts in less than three months.
A classy 82 from Shane Watson, a superb 76 from opener from Aaron Finch - featuring several cover drives - and Steve Smith's 67 looked to have laid the platform for a comfortable victory as the hosts looked well set to reach their rain-adjusted target of 275.
But an inspired spell of bowling by left-arm spinner Robin Peterson (4-32) saw Australia slump from 4-264 to 8-267 before James Faulkner (6) hit the winning runs at the start of the final over.
Watson hit two sixes and seven fours to show some timely form with the Test side for the opening match against India in Brisbane on December 4 named on Monday.
But the 33-year-old missed out on a century when he tried to take on Morne Morkel once too often and was caught at deep mid-wicket by Rilee Roussow.
Smith, who hit a match-winning century at the MCG last Friday and an unbeaten 76 in the third match in Canberra, was handed a reprieve on 20 when he was called back to the crease after being bowled by a Kyle Abbott delivery that was a no-ball.
But it was another excellent all-round display from the Sydneysider, who earlier grabbed the wicket of David Miller and took a fine catch to dismiss Farhann Behardien.
However, Glenn Maxwell, George Bailey and Matthew Wade would not have enhanced their chances by playing reckless shots to put their side in trouble.
An excellent 107 from South Africa opener Quinton de Kock and some powerful lower-order batting from Behardien (63) helped the Proteas finish on 6-280.
After a strong start the tourists' middle order struggled against some disciplined bowling, slumping from 2-164 to 5-206 with Pat Cummins continuing his good form with figures of 3-54.
Watson said he was happy to hit some form with the bat having not scored a 50 in one-day internationals for more than a year.
"It's not a great stat, is it? But it was nice get some runs, for sure," Watson said.
"I've not played too much one-day cricket over the last year and it was nice to see the good work I have been putting in to all come together."
Proteas skipper AB De Villiers, who missed the game due to a rib problem, said his side were hurting after losing the series by such a wide margin and his bowlers needed to improve their discipline.
Ten no-balls across the course of the series cost his side dearly.
De Villiers wants the problem cleared up before the start of the World Cup.
"It's unacceptable and it shouldn't happen - it's not good enough," he said.
