Williams driver Ralf Schumacher topped the times on Thursday as testing continued at the Valencia circuit in Spain.
It was Schumacher's first session of the week and he was instantly on the pace, setting a best lap of 1.10.59. He worked on determining optimum tyres and set-up for the upcoming Monaco Grand Prix.
The German's progress was hampered by an engine change required late in the afternoon after he coasted into the pits. Williams test driver Marc Gene also needed a fresh V10 after an oil leak was discovered on his car during the morning session.
Gene, who set the second best lap of the day, brought out the red flags at 11.18 local time when he ran out of fuel whilst conducting consumption work. The oil leak came to light when his car got back to the pits. The Spaniard went on to complete a long run of 32 laps as well as trying out new Michelin tyre compounds.
Jordan's Giancarlo Fisichella was third quickest behind Gene. The Italian worked on a wide-ranging programme of Monaco preparations, including electronics, cooling system and general set-up work. It was Jordan's final day of testing at Valencia.
Jenson Button was fourth fastest for Renault, the British driver working on set-up. Meanwhile, team tester Fernando Alonso's 62 laps included one long run of 20 as he carried out traction control and electronics development. Both Renault drivers stayed on after the test for promotional filming work with the team.
BAR's Olivier Panis finished fifth in the timesheets. The Frenchman brought out the red flags early in the morning when his car stopped after an experimental gearbox component on his car failed. This was promptly replaced and Panis returned to the track for further set-up work.
However, despite trying several tyre compounds a frustrated Panis was unable to match the pace of his rivals. He continues work at the circuit on Friday.
Early mists cleared at Valencia to leave sunny conditions and temperatures of up to 27°C. Track temperatures peaked at 38°C.
BAR, Renault and Williams all continue testing here on Friday. Renault and Williams are also expected to run on Saturday in a private test with tyre suppliers Michelin.