McLaren's Pedro de la Rosa topped the timesheets at Jerez today, as the Woking team experienced a day of mixed fortunes.

The Spaniard, who continued to focus on Michelin tyre testing, was driving a V10 powered MP4-20 as he completed 123 laps, posting a best time of 1:17.451. However, it was a difficult return to work for teammate Kimi Raikkonen who was sidelined for much of the day with a gearbox problem.

The Finn did not leave the garage during the afternoon session as his MP4-21 had a minor problem with the gearbox and an engine oil leak, which necessitated both components to be removed in order to complete repairs. This work took the majority of the afternoon and Raikkonen will return to the track tomorrow morning to continue his programme.

Kimi will be at the wheel of the MP4-21 for the morning of tomorrow's session, with Pedro taking over driving duties of the new car in the afternoon. Gary Paffett will join the test to drive in the MP4-20.

Renault drivers, Giancarlo Fisichella and Heikki Kovalainen, alternated on track owing to the unavailability of rear wings, but nevertheless completed their planned work for the day.

Giancarlo took to the track in the morning in very cold conditions, completing two short runs followed by three medium-distance runs before lunch. He also completed the day's running at the end of the afternoon, working on tyre testing and chassis set-up, completing a total of 76 laps.

Heikki took to the track in the second R26 in early afternoon, and also completed tyre development work with Michelin. The Finn completed 45 laps without incident.

WilliamsF1's Mark Webber was third quickest, out-pacing teammate Nico Rosberg by over a second, as the FW28, and indeed the Cosworth, continues to show good pace and reliability.

"Today Mark and Nico continued tyre testing and set-up work on the FW28s," said Sam Michael. "We had a problem with the steering rack hydraulics on Nico's car in the morning, which, unfortunately, delayed the programme while we changed it. Otherwise, we are making steady progress on reliability and set-up items. Tomorrow, Mark and Alex will be driving and will conclude the Jerez test."

Jenson Button was Honda's sole representative, beginning the day some early set-up runs before completing a tyre evaluation over long runs in the afternoon. He completed a total of 118 laps, running the V8 engine in chassis RA106-02 to its target mileage.

The team will now move to Bahrain where it intends taking advantage of the warmer climate to complete a valuable four-day test at the Bahrain International Circuit.

"We have had some issues with the engine this week," admitted Shuhei Nakamoto, Honda Racing's Engineering Director, "so we need to keep focusing on the reliability. We will have some new improvements next week on the engine that we will be running in Bahrain. Overall we are in good shape."

"Despite a difficult day on Wednesday, this has been another positive test for us," added Mark Ellis. "The pace of the RA106 has again been very encouraging and the car has been extremely reliable despite a couple of small issues. We are looking forward to next week's four-day test in Bahrain where we can fully evaluate the latest tyre developments from Michelin in realistic conditions and start our real preparations for the opening races."