Lewis Hamilton put in a late charge to claim the final P1 in pre-season testing while Red Bull and Lotus yet again ran into trouble.
The Mercedes driver posted a 1:33.278 to edge Valtteri Bottas by 0.709s. However, both drivers had their share of problems on a day mared by red flags.
On a hot day in Bahrain, Hamilton had a late start due to a gearbox issue and only emerged out on track with 20 minutes left in the morning's session.
Bottas, meanwhile, brought out the day's penultimate red flag when he stopped due to "a high-mileage failure of the internal combustion engine." He had been leading at the time.
Fernando Alonso claimed third place for Ferrari with a late lap that saw him move to just 1.002s adrift of Hamilton's P1 time. The Spaniard was another to cause a stoppage when his F14T broke down in the afternoon.
Nico Hulkenberg, who had an early shower due to an engine issue, was fourth quickest ahead of Jean-Eric Vergne and Adrian Sutil.
Sutil, who missed Saturday's running when his C33 required an engine change, was in only in action in the morning before handing the car over to team-mate Esteban Gutierrez.
The Mexican driver was eighth on the day, 9/10ths behind his team-mate, and had the dubious honour of being responsible for the final red flag of the pre-season. Gutierrez ended with 85 laps to his name.
Max Chilton separated the two Sauber drivers while Sebastian Vettel put in a very late 1:37.468 to move up from last to ninth. The German had yet another trying day as his RB10 again proved problematic.
Jenson Button also did not have the best end to his test as he stopped after lunch after 22 laps and finished down in tenth place ahead of Kamui Kobayashi, who had a "clutch problem" with his CT05.
Romain Grosjean completed the timesheets on what was another day to forget for Lotus, who will be desperately wishing that testing was not over. The Frenchman managed just 32 laps.
01 Lewis Hamilton Mercedes 1:33.278 69 laps
02 Valtteri Bottas Williams 1:33.987 +0.709 108 laps
03 Fernando Alonso Ferrari 1:34.280 +1.002 74 laps
04 Nico Hulkenberg Force India 1:35.577 +2.299 74 laps
05 Jean-Eric Vergne Toro Rosso 1:35.701 +2.423 74 laps
06 Adrian Sutil Sauber 1;36.467 +3.189 91 laps
07 Max Chilton Marussia 1:36.835 +3.557 61 laps
08 Esteban Gutierrez Sauber 1:37.303 +4.025 85 laps
09 Sebastian Vettel Red Bull 1:37.468 +4.190 77 laps
10 Jenson Button McLaren 1:38.111 +4.833 22 laps
11 Kamui Kobayashi Caterham 1:38.391 +5.113 106 laps
12 Romain Grosjean Lotus 1:39.302 +6.024 32 laps
Final Day Of Testing In Bahrain