Sebastian Vettel shrugged off a water leak to put a dampener on title rival Fernando Alonso's hopes of a championship charge.
Vettel topped both practice sessions ahead of the United States Grand Prix as the Circuit of The Americas in Austin.
The 25-year-old German finished an astonishing 1.4 seconds clear of the opposition after the opening 90 minutes around the undulating 5.513km track - the largest margin at the end of any practice outing this season.
Vettel proved it was no fluke, as, although the gap was halved in the second session, it was still a considerable cushion at a venue that should have offered more of a level playing field given this is its debut.
Mark Webber was second quickest with a time of 1:38.475 - 0.757secs adrift.
Alonso, in his Ferrari had to settle for third, just eight thousandths of a second adrift of Webber.
McLaren duo Lewis Hamilton and Jenson Button were fourth and fifth quickest, both a full second behind, followed by the second Ferrari of Felipe Massa.
