A closely contested - at least between the Mercedes drivers - second practice in Austin ended with Lewis Hamilton 0.003s ahead of Nico Rosberg.
While it appeared in the morning's session as if the Mercedes drivers would have some competition from the McLarens, that failed to materialise in Friday's afternoon session.
As the track heated up so too did Mercedes' pace with Rosberg and Hamilton holding the 1-2 on the medium tyres with the German leading the way.
Swapping to the soft Pirellis midway through the session, Rosberg retained the lead after taking almost a full second off his previous best while Hamilton slotted into second place, 0.153s down on his team-mate.
But, finding some extra pace on his second lap, the Championship leader nipped ahead, taking the lead by 0.003s. The duo were in a league of their own as both finished a full second quicker than their nearest rival.
It wasn't, however, all smooth sailing as Rosberg reported a "problem with the gearbox on the downshift" while moments later Hamilton also reported a shift issue. With 20 minutes remaining, the Brit was told to box as the team confirmed a problem with the car.
Third place went to Fernando Alonso who was a whopping 1.104s slower than Hamilton while Daniel Ricciardo in fourth was a further 0.2s down.
Felipe Massa and Kimi Raikkonen were next in line ahead of Daniil Kvyat, who continued his good form from FP1, and Kevin Magnussen.
Meanwhile, there were more problems over Red Bull, this time relating to Sebastian Vettel's car.
Moments after the FIA confirmed that the German would start Sunday's race from the pit lane due to taking a sixth engine, Red Bull announced he would miss part of FP2 as his RB10 needed a new gearbox.
He emerged 40 minutes into the session, completed 18 laps and finished down in 18th place as he opted not to push as there was no point in stressing his engine by pushing it through a qualifying simulation.
01 Lewis Hamilton Mercedes 1:39.085 18 laps
02 Nico Rosberg Mercedes 1:39.088 +0.003 33 laps
03 Fernando Alonso Ferrari 1:40.189 +1.104 29 laps
04 Daniel Ricciardo Red Bull 1:40.390 +1.305 29 laps
05 Felipe Massa Williams 1:40.457 +1.372 34 laps
06 Kimi Raikkonen Ferrari 1:40.543 +1.458 31 laps
07 Daniil Kvyat Toro Rosso 1:40.631 +1.546 32 laps
08 Kevin Magnussen McLaren 1:40.641 +1.556 37 laps
09 Jenson Button McLaren 1:40.698 +1.613 35 laps
10 Nico Hulkenberg Force India 1:40.800 +1.715 25 laps
11 Valtteri Bottas Williams 1:40.828 +1.743 36 laps
12 Romain Grosjean Lotus 1:41.054 +1.969 30 laps
13 Jean-Eric Vergne Toro Rosso 1:41.110 +2.025 35 laps
14 Sergio Perez Force India 1:41.123 +2.038 34 laps
15 Pastor Maldonado Lotus 1:41.158 +2.073 36 laps
16 Adrian Sutil Sauber 1:41.332 +2.247 32 laps
17 Esteban Gutierrez Sauber 1:41.420 +2.335 33 laps
18 Sebastian Vettel Red Bull 1:43.980 +4.895 18 laps