India crushed South Africa by 337 runs in the fourth and final Test at the Feroz Shah Kotla ground to clinch the Test series 3-0 here today. Chasing a mammoth 481, the Proteas, despite their best efforts to block every delivery, failed in their attempt to save the Test and eventually were skittled out for a paltry 143 just after the tea break.The visitors lost their last five wickets within a span of seven runs. Ashwin claimed his 15th five wicket haul of his Test career to send the Proteas on the backfoot. He was adjudged the Man-of the-series for his brilliant bowling in the entire series.The visitors went for the tea-break at 136 for five with Dane Vilas giving overnight batsman AB de Villiers company. Post-tea session Umesh Yadav got wicket of Dane Vilas. Then Ashwin dismissed de Villiers by off-break. His marathon innings of 43 runs came off 297 deliveries and composed of six fours. Yadav once again struck as he got the wickets of Kyle Abbott and Dane Piedt. Ashwin then completed the formalities as he got his fifth wicket removing last man Morne Morkel.Earlier, resuming the day at 72 for two, South Africa continued their dead-batting as they scored just 22 runs in 35 overs to reach 94 for three at lunch. Team India skipper Virat Kohli has now won both his first two Test series. India had won the first Test by 108 runs at Mohali and the third match by 124 runs in Nagpur. The second match at Bengaluru was called off.