Sebastian Vettel completed a practice clean sweep to again leave his rivals in the shade ahead of Sunday's United States Grand Prix.
Up until the final minutes it appeared as if McLaren would turn the tables on Red Bull after Vettel and Mark Webber formed a one-two on Friday as Lewis Hamilton and Jenson Button led the way at the top of the timesheet.
Vettel, however, had other ideas as he conjured the fastest lap yet at the Circuit of the Americas as the United States makes its Formula One return this weekend after a five-year absence.
On the occasion of his 100th grand prix, on current evidence Vettel appears poised for another pole position as he initially opened up a full-second gap with a lap time of one minute 36.490secs.
Come the conclusion, Hamilton at least managed to close that gap to 0.258secs, with Williams' Pastor Maldonado again in close attendance as the Venezuelan was half a second adrift.
Ferrari's Fernando Alonso, 10 points adrift of Vettel and needing to finish within 15 or better on Sunday to ensure the championship fight goes down to the wire in Brazil next weekend, was 0.690secs down in fourth.
From second late on, Button plummeted to 10th, finishing 1.048secs behind Vettel, who has in his sights the prospect of becoming only the third driver in F1 history to win three successive titles.
Mercedes' Nico Rosberg, Felipe Massa in his Ferrari, Sauber's Sergio Perez and Nico Hulkenberg for Force India, all managed to get ahead of Button in the dying stages.