Rubens Barrichello put Williams on top of the times at the Jerez circuit on Thursday, as poor weather conditions continued to hamper the teams' preparations for the start of the season.
The session started on a damp track, and despite spells without rain, the asphalt was never completely dry during the day.
Barrichello set his best time around lunch time, when the conditions were at its best, and stayed there as rain made its return moments later.
The rain came and went throughout the rest of the day, making sure that the track conditions were far from ideal until the chequered flag was waved.
Renault's Vitaly Petrov also made the most of the conditions around 1pm to post the second quickest time, ahead of yesterday's pace-setter Sebastian Vettel, who completed 70 laps with the Red Bull.
Nico Rosberg was fourth quickest for Mercedes GP, with Felipe Massa rounding up the top five in the Ferrari.
Virgin Racing had a much more productive day than yesterday, when Timo Glock managed just 10 laps. Today the German driver completed 72 on his way to the eighth fastest time of the day.
Glock's session, however, was not trouble-free, as he caused two red flags when he went off the track.
The Lotus team, who enjoyed a very promising day on its T127's maiden run yesterday, was not so lucky today when Heikki Kovalainen took over from third driver Fairuz Fauzy.
The Finn lost control of his car around 1pm and made contact with the tyre barriers, damaging the front wing. With Lotus not having a spare part on track, the team was forced to miss the remaining part of the session, having completed just 30 laps.
Kovalainen admitted afterwards that he had simply made a mistake and was sorry for the valuable time lost.
Pedro de la Rosa and his Sauber team were worse off, however, as the Spaniard completed just eight laps in the morning and never returned to the track, the team deciding it was not worth running.
"With the same mixed conditions as yesterday, it simply wasn't worth doing much driving today," de la Rosa said. "We have a good understanding of the car, and I'm looking forward to the next test in Barcelona, hopefully on a dry track."
Toro Rosso's Sebastien Buemi also had a frustrating day, finishing as 11th fastest after being hit by a hydraulic problem.
"The bad weather meant we could not get through all of our planned programme for today and we also lost a bit of time with a hydraulic problem," he said. "So, it's a bit disappointing, but now I'm looking forward to the Barcelona test and hopefully some dry running."
There were a total of four red flags during the session: two caused by Glock, one by Kovalainen and another one by Barrichello.
Pos Driver Team Time Laps 1. Barrichello Williams-Cosworth (B) 1:27.145 98 2. Petrov Renault (B) 1:27.828 56 3. Vettel Red Bull-Renault (B) 1:28.162 70 4. Rosberg Mercedes GP (B) 1:28.515 71 5. Massa Ferrari (B) 1:28.879 92 6. de la Rosa BMW-Sauber (B) 1:29.691 8 7. di Resta Force India-Mercedes (B) 1:30.344 33 8. Glock Virgin-Cosworth (B) 1:30.476 72 9. Liuzzi Force India-Mercedes (B) 1:30.666 24 10. Hamilton McLaren-Mercedes (B) 1:31.633 57 11. Buemi Toro Rosso-Ferrari (B) 1:32.678 57 12. Kovalainen Lotus-Cosworth (B) 1:33.554 30 All Timing Unofficial