Aaron Finch only just missed out on fastest ever one-day international half-century and George Bailey also put on a show after John Hastings set Australia up for a six-wicket win to seal a series triumph over Sri Lanka.
Finch (55) reached 50 in only 18 balls, just two shy of the record set by AB de Villiers, to equal the quickest half-century by an Australia batsman in an ODI and the in-form Bailey made 90 not out as the tourists reached their victory target of 213 with 19 overs to spare in Dambulla.
All-rounder Hastings took 6-45 and Dhananjaya de Silva (76) was the only Sri Lanka batsman to make a significant contribution in their total of 212 all out.
Angelo Mathews (40) suffered a calf injury while batting and the captain was unable to bowl as Australia took a 3-1 lead with one game to come in Pallekele on Sunday.
Mitchell Starc (1-51) trapped teenage debutant Avishka Fernando lbw without scoring and Sri Lanka were in the mire on 31-3 when Scott Boland (1-36) had Dinesh Chandimal (5) caught behind.
De Silva and Mathews combined for a much needed stand of 84, with the opener playing some elegant strokes to make his maiden ODI half-century.
Sri Lanka were dealt a big blow when Mathews had to retire hurt after injuring himself taking a run and De Silva's innings, which featured nine boundaries, was ended by the impressive Hastings.
A procession of wickets followed, with Mathews returning to the crease limping heavily but still able to add a couple of late boundaries almost on one leg before he became Hastings' sixth victim from the final ball of the innings.
Finch was in no mood to hang around, starting his innings with four boundaries from as many balls off Amila Aponso and taking 18 off the next over from Thisara Perera in a brutal onslaught.
The powerful Finch matched the Australia ODI record set by Simon O'Donnell in 1990 when he was raising his bat after facing only 18 balls - hitting three sixes and eight fours - before Sachith Pathirana (3-37) saw him on his way.
Australia were 100-3 from only 8.1 overs after David Warner (19) and the recalled Usman Khawaja (0) were dismissed, but Bailey made a second successive half-century and Travis Head (40) chipped in before Matthew Wade hit Dilruwan Perera (1-69) for six to seal victory.