The German, looking to close a 29-point deficit to championship leader Fernando Alonso, has led the field away in each of the last three races here, and suggested a repeat could be likely in qualifying on Saturday as he topped the morning practice times with a lap of one minute 32.136 seconds.
His team-mate Mark Webber, quickest in Friday's running, was second, just over two-tenths of a second back.
McLaren have looked to be Red Bulls' closest rivals for victory this weekend, but they were not able to show their outright pace.
Jenson Button, still looking to recover after taking a wrong turn on set-up on Friday afternoon, could only manage the eighth best time while Lewis Hamilton was 13th after a frightening incident late in the hour-long session.
The 2008 world champion, on his way to Mercedes next year, was on his quickest lap when he came across the dawdling Marussia of Charles Pic travelling slowly on the racing line on the entry to the chicane.
Hamilton's closing speed forced him to dramatically jink to his right to avoid a huge accident, and he quickly got on the radio to tell his team, "I want to let (race director) Charlie (Whiting) know just how dangerous that last corner was."
Felipe Massa, fighting to secure his future with Ferrari, was third quickest, ahead of Michael Schumacher in his Mercedes.
The Saubers of Sergio Perez and Kamui Kobayashi were fifth and sixth, ahead of Romain Grosjean and Button.
Paul Di Resta was ninth as he recovered from his costly off on Friday, with Pastor Maldonado rounding out the top 10.
Alonso could only manage 11th as Ferrari again struggle to get anywhere near Red Bull and McLaren, with his championship lead evaporating.
Nico Hulkenberg undid his good work of Friday, when he finished the day fourth, by crashing his Force India at the Degner curves, taking the front left corner off the car and leaving his mechanics with a lot of work to do to get him ready for qualifying.