Mark Webber and his Red Bull Racing team returned to the top of the timesheets at Jerez as the weather finally gave the teams a break on Friday.
After days of rain, the sun finally made an appearance for most the session, allowing teams to work on their programmes following the frustration of the opening two days.
Australian Webber set the best time of the day, and of the week so far, after a lap of 1:19.299 early in the afternoon. His time was also the best at Jerez this year, nearly two tenths of a second quicker than last week's benchmark, set by McLaren's Lewis Hamilton.
Webber's day was not without trouble, however, the Red Bull driver causing the fourth red flag of the day when he stopped around midday.
Fernando Alonso, taking over from team-mate Felipe Massa in the cockpit of the Ferrari F10, finished as second quickest on a day where the Italian squad made good use of the conditions to make up for the time lost over the last two days.
The Spaniard managed 132 laps without any problems and finished over eight tenths behind Webber.
World champion Jenson Button began his week's work today and posted the third quickest time with the McLaren. Nico Hulkenberg and Michael Schumacher completed the top five.
Newcomers Virgin and Lotus had their share of problems today, causing a total of three red flags between the two. Heikki Kovalainen stopped on track around 9:50am due to a clutch sensor failure, but the Finn returned to work later on and managed a total of 68 laps on his way to the slowest time of the day.
At Virgin, Lucas di Grassi took over from team-mate Timo Glock, the Brazilian causing two stoppages due to problems with his car.
There was some encouragement for both teams, however, as Glock and Kovalainen finished the day around four seconds off the pace.
The Sauber team had a miserable day after Kamui Kobayashi stopped on track with a fuel system problem just two hours into the session.
It took the Japanese driver some five hours to return to the track to complete just 28 laps for the eighth quickest time.
A total of six red flags hindered progress today: two by di Grassi, one by Webber, one by Kobayashi, one by Kovalainen and the final one by Hulkenberg, who caused the session to end five minutes early when his Williams stopped on track.
Testing resumes tomorrow.
Pos Driver Team Time Laps 1. Webber Red Bull-Renault (B) 1:19.299 115 2. Alonso Ferrari (B) 1:20.115 132 3. Button McLaren-Mercedes (B) 1:20.394 101 4. Hulkenberg Williams-Cosworth (B) 1:21.432 138 5. M.Schumacher Mercedes GP (B) 1:21.437 79 6. Kubica Renault (B) 1:21.916 100 7. Sutil Force India-Mercedes (B) 1:21.939 69 8. Kobayashi BMW-Sauber (B) 1:22.228 28 9. Alguersuari Toro Rosso-Ferrari (B) 1:22.564 120 10. di Grassi Virgin-Cosworth (B) 1:23.504 34 11. Kovalainen Lotus-Cosworth (B) 1:23.521 68 All Timing Unofficial