Lewis Hamilton set the fastest time seen this week in Bahrain to top the timesheets on Day Three at the Sakhir circuit.
Replacing team-mate Nico Rosberg for the day, Hamilton crossed the line with a 1:35.812 to lead the way after the first two hours of running.
The Mercedes driver, who was working on set-up, continued to put in the laps before lunch and lowered the benchmark on three occasions to bring his P1 time down to a 1:34.263.
That stood as the time to beat at midday with neither the Brit nor his rivals managing to do so as the hours counted down.
Hamilton's 1:34.263 also set a new benchmark for the week, seven-tenths up on Kevin Magnussen's P1 time from Thursday.
The Dane, though, was not on hand to defend as he handed the MP4-29 over to the newly-engaged Jenson Button, who completed a marathon 103 laps on the day.
The Brit finished second quickest, 0.713s behind Hamilton while a late dash from Felipe Massa put him up into third place.
The new Williams driver was only in action in the afternoon as Valtteri Bottas had the car in the morning during which he focused on practice starts and pit stops, covering 55 laps without a time.
Meanwhile, Esteban Gutierrez, who covered 96 laps, was fourth quickest in the Sauber having edged Sergio Perez while a 1:37.476 in the final hour saw Kimi Raikkonen move up to sixth place.
Daniil Kvyat was seventh for Toro Rosso finishing ahead of Pastor Maldonado, who made his official Lotus debut and stopped twice on track, and Red Bull's Daniel Ricciardo.
It was another dismal day for Red Bull with Ricciardo completing just 28 laps before a mechanical problem put him out of the running.
Marcus Ericsson, who did 98 laps in his Caterham, was tenth ahead of Max Chilton who managed just four laps due to a fuel system problem.
01 Lewis Hamilton Mercedes 1:34.263 67 laps
02 Jenson Button McLaren-Mercedes 1:34.976 +0.713 103 laps
03 Felipe Massa Williams-Mercedes 1:37.066 +2.803 60 laps
04 Esteban Gutierrez Sauber-Ferrari 1:37.180 +2.917 96 laps
05 Sergio Perez Force India-Mercedes 1:37.367 +3.104 57 laps
06 Kimi Raikkonen Ferrari 1:37.476 +3.213 44 laps
07 Daniil Kvyat Toro Rosso-Renault 1:38.974 +4.711 57 laps
08 Pastor Maldonado Lotus-Renault 1:39.642 +5.379 26 laps
09 Daniel Ricciardo Red Bull-Renault 1:40.781 +6.518 28 laps
10 Marcus Ericsson Caterham-Renault 1:42.130 +7.867 98 laps
11 Max Chilton Marussia-Ferrari 1:46.672 +12.409 4 laps
12 Valtteri Bottas Williams-Mercedes no time 55 laps
Day Three's Action In Bahrain