Lewis Hamilton made a statement of intent ahead of Sunday's Hungarian Grand Prix by beating Mercedes team-mate Nico Rosberg in first practice.
Hamilton, who has won this race four times in seven years, is keen to eat into Rosberg's 14-point championship lead before the summer break.
The two traded fastest times until Hamilton ended up 0.183 seconds ahead.
Ferrari's Kimi Raikkonen and Fernando Alonso were third and fourth, ahead of Red Bull's Sebastian Vettel.
Unusually, Raikkonen was quicker than team-mate Alonso, who has out-qualified him eight times in 10 races this year and beaten him at every one.
But the Finn, who said at the German Grand Prix last weekend that he had been more comfortable with the feel of the car, ended the first session 0.451secs clear of the Spaniard. Raikkonen was 0.607secs slower than Hamilton's pace-setting lap of one minute 25.814 seconds.
Kevin Magnussen of McLaren was sixth, ahead of Toro Rosso's Jean-Eric Vergne and Red Bull's Daniel Ricciardo, whose running was restricted by a problem with the energy store of his car's hybrid system.
McLaren's Jenson Button was ninth, 0.447secs slower than team-mate Magnussen, and complained of poor rear grip.
Williams's Felipe Massa was 10th, while in the second Williams Valtteri Bottas, who has been on the podium for the past three races, was 14th.
BBC F1 analyst Allan McNish said: "In the last couple of Fridays, Williams have worked very hard to make sure their race pace is strong so I expect them to come up, but apart from that I don't expect the order to change too much."
However, Ferrari have tended to be quicker on Fridays than for the rest of the weekend, so can be expected to slip back a little in qualifying and the race.
Alonso said on Thursday that he expected the team to be in about the same place as usual - qualifying around sixth or seventh and battling up to fourth or fifth in the race.
Several drivers ran wide on the slippery track, which is always dusty from a lack of use on the first practice day at the grand prix.
Marussia's Max Chilton had a troubled session, his car returning to the pits with smoke and flames pouring from the rear after his installation lap following an oil leak.
He managed only five laps, but was still quicker than team-mate Jules Bianchi, who was 22nd and last.