Vettel, who was fastest in FP1 and FP 2 yesterday, clocked 1:25.842 to emerge fastest and was followed by McLaren's Jenson Button, who was 0.192 second behind at the Buddh International Circuit.
In every session, the defending champion has gone on to improve his previous best lap time. He had managed 1:26.221 in FP2 yesterday and 1:27.619in FP1.
His team-mate Mark Webber (1:26.108) was third while Lewis Hamilton put the second McLaren in the fourth position with a timing of 1:26.108.
Surprisingly, Finnish Kimi Raikkonen and Bruno Senna pushed Ferrari's Fernando Alonso to seventh by finishing ahead of him.
Sahara Force India's Nico Hulkenberg continued to improve and was eighth after clocking his fastest lap in 1:26.531 and was followed by Mercedes' Michael Schumacher and Romain Grosjean of Lotus.
Paul di Resta continued to struggle in the second Force India, managing 1:27.193 for 14th position.
The lone Indian driver Narain Karthikeyan (1:30.873) finished 23rd ahead of his HRT teammate Pedro de la Rosa.
