Sri Lanka 307 for 4 (Dilshan 99, Sangakkara 75*, Thirimanne 68) beat South Africa 179 (De Villiers 51, Lakmal 3-24, Mendis 3-36) by 128 runs
Scorecard and ball-by-ball details
South Africa suffered a fifth successive sub-standard batting performance in Sri Lanka to concede the final match in the series - a dead rubber - to opposition who have shown their superiority. Throughout the 12-day contest, Sri Lanka batted with more authority and bowled with more intent and just to emphasise that, they did both even better today despite resting three senior players.
Tillakaratne Dilshan followed up his century in the previous match with 99 and shared in a second-wicket stand of 163 with Lahiru Thirimanne who found confidence with a half-century, while Kumar Sangakkara racked up milestones. He overtook Misbah-ul-Haq as the leading run-scorer in ODIs this year and become the top-scorer for Sri Lanka in a bilateral series with 372 runs. With all those accolades, his best mate, Mahela Jayawardene was hardly missed.
Neither was Sri Lanka's marquee fast bowler, Lasith Malinga, or leading spinner Rangana Herath. Their replacements, Suranga Lakmal and Sachithra Senanayake, did the damage with five wickets between them to ensure even the flicker of a challenge South Africa posed was suffocated before it find any oxygen.
Although South Africa have scored more runs in each innings as this series wore on, they were always unlikely to chase down a score of 300-plus. They have a lethargic bowling performance and indifferent showing in the field to thank for being asked to do that.
Morne Morkel and Lonwabo Tsotsobe started well with probing lines outside offstump and had early success. They kept Sri Lanka's scoring rate under four an over and Morkel had Kusal Perera out when the opener bottom-edged to Quinton de Kock.
What South Africa should have used as an opening, Sri Lanka grabbed onto as an opportunity. They moved Thirimanne up the order and he responded by building steadily alongside Dilshan.
They pair gave themselves time against South Africa's ineffectual spin duo so that when Morkel was brought back, he posed little threat. Dilshan reached his half-century with a backfoot drive off him, while Thrimanne's came with a single off Phangiso. By the halfway mark, they were consistently scoring more than four runs an over and had laid enough foundation to up the aggression.
And they did. The very next over, Thirimanne charged Phangiso and drove Morkel with confidence. He could have been stumped for 62 but Quinton de Kock missed the chance. It only cost six runs before JP Duminy took a tumbling catch to see Thirimanne out but illustrated a wider South African problem.
Their fielding was not up to scratch, they didn't back up enough, their throws were wayward and de Villiers' communication in changing his fields was almost non-existent. All this while Sangakkara arrived and smoked Duminy back over his head and hit Morkel of all of his lengths. The three fours that came in the over where off a good length ball, a full one and a short one.
Sangakkara missed out on a century the last time he batted with Dilshan but this time it was Dilshan's turn to suffer that fate. He marched into the 90s with an authoritative pull and lingered on 99 for three balls before he was bowled by a McLaren slower ball.
In celebration of his wicket, South Africa seemed to forget all their plans. Tsotsobe reverted back to short balls and Morkel could not find any workable line or length. His figures were the most expensive of his career. Mathews let loose and Thisara Perera had licence to go wild but it was Sangakkara's presence that made a score over 300 possible.
He smacked 49 runs on the on-side and helped himself to extravagant shots like scoops over de Kock's head. He was largely responsible for the addition of 52 runs in the last five overs and for South Africa's mountain being too high.
They started gallantly, with de Kock showing his promise with powerful cuts, and 32 runs scored off the first five overs. He remained loose outside the offstump and when he left a gap between bat and pad against Senanayake, he was bowled. The 35 he put on with Hashim Amla was South Africa's highest opening stand of the series.
Amla and Duminy put on 25 before Amla also failed to read Senanayake and was plumb lbw. Dumimy padded up to Dilshan and Faf du Plessis' lean run grew longer when was caught. At 69 for 4, South Africa were only headed one way.
De Villiers scored a-run-a-ball 51 but was caught at point on his first attempt to lash out. South Africa they were eventually put out of their misery in the 44th over to hand Sri Lanka a 4-1 win and leave themselves with more questions than answers about the rebuilding of their one-day unit.

Firdose Moonda is ESPNcricinfo's South Africa correspondent