Michael Schumacher impressed in the first practice sessions of his comeback in Bahrain ahead of Sunday’s Grand Prix.
Mercedes GP team-mate Nico Rosberg finished first and the seven-times Formula One champion third, at the end of Friday's two practice sessions.
Rosberg was the top of the timesheets overall at the Sakhir circuit with a lap of one minute 55.409 seconds, with Schumacher less than half a second adrift of his fellow German.
McLaren's Lewis Hamilton was second, though the aerodynamic device his car is using may be the subject of protests after the race.
Hamilton or team-mate Jenson Button can close off a vent in the cockpit of their car using their legs, which allows stalling of the rear wing for extra straight-line speed.
FIA race director Charlie Whiting passed the device as legal, but opposing teams are likely to complain about its use after the race.
With reigning world champion Button fourth quickest, 0.667secs behind Rosberg, Mercedes-powered cars took the top four places.
Last year’s championship runner-up Sebastian Vettel was fifth in his Red Bull, whilst Williams’ debutant Nico Hulkenberg was sixth.
Ferrari's Felipe Massa was seventh, with team-mate Fernando Alonso ninth, sandwiching Renault's Russian tyro Vitaly Petrov.
Of the newcomers at the bottom of the grid, the Lotus pair of Heikki Kovalainen and Jarno Trulli finished 18th and 19th, edging out Virgin Racing's Timo Glock and Lucas di Grassi.