Sebastian Vettel headed Mark Webber in a Red Bull one-two in first practice at the Hungarian Grand Prix.
The world champion was 0.259 seconds quicker than the Australian, with Vettel's title rivals Kimi Raikkonen and Fernando Alonso third and fourth.
Raikkonen was 0.287secs off Vettel in the Lotus, with Alonso's Ferrari a further 0.089secs adrift.
Vettel holds a 34-point lead over Alonso, who says he cannot afford to let the German extend his advantage.
The second Lotus of Romain Grosjean was fifth, ahead of McLaren's Jenson Button, Adrian Sutil's Force India and the Mercedes of Nico Rosberg.
McLaren's Sergio Perez was ninth, while Scot Paul Di Resta was 18th in the other Force India.
Lewis Hamilton was 13th in the second Mercedes, as the team attempted to get to grips with the new Pirelli tyres that have been introduced for this race.
Hamilton did a long run trying to assess the durability of the tyre on the Mercedes, which has struggled with excessive tyre usage this season.
The new tyres are of a different construction as Pirelli tries to prevent a repeat of the series of failures at the British Grand Prix.
Raikkonen pitted before the end of the session after his team said "puncture" to him over the radio, but there appeared to be no problems with the Finn's tyres.
Vettel appeared to be in very strong shape. He managed a time towards the end of the session that was only 0.2secs off his best.
"Red Bull really seem to have got on top of this revised tyre. They are looking pretty strong," said BBC F1 technical analyst Gary Anderson.