US GP: Sebastian Vettel leads as Nico Hulkenberg stars in practice

Friday pacesetter Vettel took little time to hit the front again on Saturday morning with an early 1m37.433s lap.

That kept him in front until everyone switched to medium tyres and qualifying simulations for the final few minutes.

Hulkenberg found the most impressive gain on the softer Pirellis, going top with a 1m37.356s and then improving his pace to a 1m37.272s after a cool-down lap.

He resisted one challenge when Webber hit traffic on his first medium-tyre run.

But Vettel had no such dramas and a 1m36.733s lap put him comfortably on top.

Webber then got between the two Germans to take second with his final lap, which was 0.203 seconds off Vettel's pace.

Lewis Hamilton's Mercedes ultimately pushed Hulkenberg down to fourth.

Romain Grosjean turned the tables on new Lotus team-mate Heikki Kovalainen after the Finn's strong start on Friday, taking fifth to the newcomer's 13th. The pair were half a second apart.

McLaren had an encouraging session, as Jenson Button and Sergio Perez took sixth and eighth, split by Mercedes driver Nico Rosberg.

Williams also had reason to smile, with Valtteri Bottas beating Adrian Sutil to ninth.

Conversely Ferrari had a troubled morning, lacking pace on both tyre compounds. The best Fernando Alonso could manage was 11th place.

 Pos  Driver               Team/Car              Time       Gap      Laps
  1.  Sebastian Vettel     Red Bull-Renault      1m36.733s           14
  2.  Mark Webber          Red Bull-Renault      1m36.936s  +0.203s  20
  3.  Lewis Hamilton       Mercedes              1m37.064s  +0.331s  22
  4.  Nico Hulkenberg      Sauber-Ferrari        1m37.272s  +0.539s  20
  5.  Romain Grosjean      Lotus-Renault         1m37.345s  +0.612s  20
  6.  Jenson Button        McLaren-Mercedes      1m37.534s  +0.801s  18
  7.  Nico Rosberg         Mercedes              1m37.578s  +0.845s  24
  8.  Sergio Perez         McLaren-Mercedes      1m37.583s  +0.850s  19
  9.  Valtteri Bottas      Williams-Renault      1m37.747s  +1.014s  17
 10.  Adrian Sutil         Force India-Mercedes  1m37.748s  +1.015s  21
 11.  Fernando Alonso      Ferrari               1m37.763s  +1.030s  16
 12.  Esteban Gutierrez    Sauber-Ferrari        1m37.774s  +1.041s  18
 13.  Heikki Kovalainen    Lotus-Renault         1m37.879s  +1.146s  21
 14.  Pastor Maldonado     Williams-Renault      1m38.022s  +1.289s  16
 15.  Daniel Ricciardo     Toro Rosso-Ferrari    1m38.109s  +1.376s  23
 16.  Paul di Resta        Force India-Mercedes  1m38.275s  +1.542s  22
 17.  Felipe Massa         Ferrari               1m38.408s  +1.675s  17
 18.  Jean-Eric Vergne     Toro Rosso-Ferrari    1m38.636s  +1.903s  21
 19.  Charles Pic          Caterham-Renault      1m39.578s  +2.845s  19
 20.  Giedo van der Garde  Caterham-Renault      1m40.056s  +3.323s  21
 21.  Jules Bianchi        Marussia-Cosworth     1m40.825s  +4.092s  21
 22.  Max Chilton          Marussia-Cosworth     1m41.293s  +4.560s  18