Once again, unpredictable weather conditions caused problems for the nine teams running at Valencia, forcing them to adapt their programmes accordingly. Nonetheless, Fernando Alonso continued to set the pace, though the Renaults, and Kimi Raikkonen's Ferrari weren't far behind.

Despite clear skies in the morning, the track was still wet from overnight rain and took a long time to dry out. Consequently, McLaren, like many of its rivals, opted to continue with wet weather tyre testing.

Pedro de la Rosa took to the track shortly before 14:00, running the MP4-22 crashed by Lewis Hamilton last week. The Spaniard joined his teammate in the on-going development schedule with both drivers finally getting to run on dry tyres.

By 15:30 however, the rain had begun to fall again and this saw the team return to wet tyres for the remainder of the session.

Following an installation lap when the circuit first opened, the two Renaults then waited for the track to improve before beginning their programme. A sunny spell around 13:00 meant the track was finally good enough for some meaningful running.

Both drivers began long runs at this time in order to assess the handling of the R27 on the 'green' track, and to collect as much data as possible. With start simulations and refuelling in the pit-lane, the goal was once again to cover a race distance with each car.

However, a mechanical failure on Fisichella's car during the afternoon forced the Roman to cut short his running. And when it began to rain again during the afternoon, the team decided to save Kovalainen's programme for tomorrow in the expectation of improved conditions. The day's work was therefore disrupted, but the team was remains pleased with the car's performance.

"The weather dictated our running once again today," said Fisichella. "We waited for a long time, which ate into our programme, but these things happens. I had a mechanical problem but I'm not worried - the team is working to find out what happened, and it is always better to have these problems in testing… We will carry on with the programme tomorrow, hopefully with some better weather!"

"The track conditions today were changing all the time, and quite tricky," added Kovalainen, "but we still made some progress with our work. We need to carry on in the same direction tomorrow, and hopefully we can do more laps. The performance of the car seems OK, but we want to put more miles on it - and we need better weather to do so!"

Felipe Massa joined Kimi Raikkonen, the Brazilian running the 248 F1, concentrating mainly on the development of new components, while the Finn continued with the F2007. Kimi waited until the track dried in order to resume his development programme, but the raid during the afternoon was enough to significantly affect the planned programme.

Nick Heidfeld was joined by Robert Kubica, both drivers running the Bavarian outfit's 2007 car. Originally, the team had planned to concentrate on set-up scanning and aerodynamic development, but the conditions made this difficult. Consequently, the team had to be flexible and swapped to a tyre and electronical systems evaluation programme.

Late in the day, a hydraulic leak caused a fire on Kubica's car, though it did not do too much damage. His teammate didn't have an entirely trouble free day, a mechanic failure resulting in one of several red flag periods that permeated session.

After his strong showing yesterday, Jarno Trulli was joined by Ralf Schumacher, who returned to the wheel of the TF107 for the first time since the car's initial shakedown runs.

When track conditions improved and grooved tyres could be used, both Jarno and Ralf began their work on perfecting the set-up of the new car, trying different combinations as they look to get the best out of the TF107.

"We had damp conditions in the morning so we had to wait a while before we could go out," said the German. "After that is was a good day and we made some good progress. We had to stop a little early because of the rain unfortunately, there was no point continuing in those conditions. The car felt good again, just as it did on the first day I drove it at Paul Ricard for the shakedown. I must say it seems to be a step forward but we have to wait a little longer to see what the others are up to."

"Today went pretty well," added Trulli, "and we managed to get a lot of work done but we had to stop a little bit early because of the rain. There was no point going out on a wet track as that would have been a waste of tyres. I had a good feeling again with the car and I am optimistic about it, but it is still too early to really understand how much potential it has. It has been a good day and I am happy we have made some more progress."

Barrichello and Rossiter continued for Honda. The Brazilian, in the new RA107 car, went out for a short time in the morning session to work through an evaluation of the Bridgestone wet weather tyres. With the track drying out by early afternoon, he went on to complete some dry tyre runs, covering a total of 73 laps.