Sebastian Vettel set a best time of 1m 37.305 on the medium compound tyre to finish 0.115s ahead of his Australian team mate Mark Webber on 1m37.420s.
Sebastian Vettel and Mark Webber might have kept Red Bull's powder dry in FP1, but in Friday afternoon's second practice session at Austin's Circuit of The Americas they saw off all competition.
Vettel set a best time of 1m 37.305 on the medium compound tyre to finish 0.115s ahead of his Australian team mate on 1m37.420s. The Mercedes duo of Nico Rosberg and Lewis Hamilton got closest, but they were another 0.480s and 0.653s further back respectively. Hamilton was driving with a new chassis after a pre-event inspection revealed two large cracks in the old one.
Kimi Raikkonen's replacement Heikki Kovalainen demonstrated his mettle with the fifth fastest time of 1m 38.073s for Lotus, right behind his former McLaren team mate Hamilton and ahead of current partner Romain Grosjean, who was two tenths of a second adrift back in eighth. The two Saubers sat between the black and gold cars, with Esteban Gutierrez shading Nico Hulkenberg with 1m 38.229s to 1m 38.254s. Grosjean lapped in 1m 38.255s.
Jenson Button and Fernando Alonso completed the top 10, the Briton lapping his McLaren in 1m 38.269s, the Spaniard his Ferrari in 1m 38.461s. Shortly before the second session began, Button was handed a three-place grid penalty for overtaking Toro Rosso's Daniil Kvyat during the red flag period in FP1.
Adrian Sutil, Felipe Massa and Sergio Perez completed the runners beneath 1m 39s. The Force India pilot lapped in 1m 38.719s, the Brazilian in 1m 38.938s in his Ferrari and the Mexican in 1m 38.941s in his McLaren.
Daniel Ricciardo was 14th for Toro Rosso on 1m 39.246s, heading Force India's Paul di Resta on 1m 39.410s, while Williams dropped back after their impressive morning showing. Valtteri Bottas was 16th on 1m 39.512s to head Jean-Eric Vergne on 1m 39.579s for Toro Rosso, and his own team mate Pastor Maldonado on 1m 39.784s.
Charles Pic assumed control at Caterham as Giedo van der Garde took his car back from impressive American rookie Alexander Rossi after FP1, but the two were close. The Frenchman lapped in 1m 40.376s, the Dutchman 1m 40.563s.
Marussia were a long way off the pace at the back of the pack. Max Chilton lapped in 1m 46.226s before he spun his car at the final corner late in the session. Team mate Jules Bianchi was even further back after taking his car back from Rodolfo Gonzalez. The Frenchman's best time was 1m 47.009s.