Wins in Singapore, Japan and Korea have helped Vettel reel in Ferrari's Fernando Alonso, with the German edging six points clear of the Spaniard as the two men chase a third Formula One world title.
Vettel managed to find a further four tenths of a second compared to his best lap of Friday, clocking one minute 25.842secs for the 5.125km Buddh International Circuit on the outskirts of New Delhi.
As for Alonso, the 31-year-old is struggling to make any inroads on Vettel because after finishing six tenths of a second adrift Friday, the gap had widened slightly to 0.679secs at the end of the hour-long final practice session.
That left Alonso down in seventh place, behind both McLarens and Vettel's Red Bull team-mate Mark Webber, as well as Kimi Raikkonen in his Lotus and the surprise package of Bruno Senna for Williams.
The team having made most gains overnight are McLaren as Jenson Button and Lewis Hamilton found themselves just under a second down yesterday.
But come the conclusion to FP3, Button had cut that gap to 0.192secs, whilst Hamilton was 0.309secs adrift, with Webber sandwiched between the duo at 0.266secs down.
Behind the leading quartet were Raikkonen, still in with an outside chance of the title as the Finn trails Vettel by 52 points, although he remains without a win all year.
Raikkonen was a third of a second down, with Senna a further five thousandths of a second behind, followed by Alonso.
Force India's Nico Hulkenberg clearly has the edge on team-mate Paul di Resta this weekend, with the German eighth on the timesheet, six places and half a second up on the Scot.
Mercedes' Michael Schumacher and Romain Grosjean in his Lotus completed the top 10, with Ferrari's Felipe Massa 11th, and the last of those within a second of Vettel.
As at Force India, there is a clear discrepancy at Williams as Pastor Maldonado finds himself comfortably trailing Senna, on this occasion by almost a second, with the Venezuelan 12th quickest.
Either side of Di Resta in 14th were Sauber's Sergio Perez and Nico Rosberg in his Mercedes, with the German 1.367secs off the pace.
At the rear, five seconds down, was Pedro de la Rosa in his HRT, a fraction behind the only Indian on the grid in team-mate Narain Karthikeyan.