WilliamsF1's Mark Webber was quickest as testing kicked off at Valencia today.

The Australian was joined by Alexander Wurz, both men at the wheel of FW28s.

Red Bull appear to have solved the overheating problem that has plagued the team in recent tests, Christian Klien completing 100 laps in a brand new RBR2, and finishing just 0.563s off Webber's time. The Austrian was joined by Robert Doornbos, who drove the other RBR2.

Klien's car was fitted with the aerodynamic configuration parts it will use for the first race of the season in Bahrain, featuring a revised bodywork package.

"We ran cooling configurations and also worked on chassis set-up" commented Technical Director, Mark Smith.

Doornbos concentrated on set-up work and development of the car's control systems.

Klien continues in the brand new car tomorrow, with Doornbos running for the morning in No. 1 before handing over the controls to David Coulthard in the afternoon.

Pedro de la Rosa was the quicker of the two McLaren drivers on duty, the Spaniard, and teammate, Juan Pablo Montoya, both driving brand new MP4-21s, which arrived from the McLaren Technology Centre over the weekend.

Work for both drivers focused on initial systems checks, prior to proper testing with the two cars starting tomorrow.

Pedro completed 100 laps of the 3.94km circuit, putting over 400km on his MP4-21, including two long runs of 26 laps. The Spaniard set a quickest time of 1:11.619, during a run of 10 laps mid-afternoon, which put him third on the timesheets for the day.

Juan Pablo covered 190km during today's session in the other MP4-21. He ended the day fourth on the timesheets, with a 1m11.700, having completed 50 laps over a series of multi-lap runs, including a 15-lap stint at the end of the day. He started running shortly before 14:00, as the test team had been completing the engine and gearbox installation.

Kimi Raikkonen will join Juan Pablo on track tomorrow (Wednesday).

Midland had three drivers on duty, with Tiago Monteiro at the wheel of the new M16, while Markus Winkelhock and Giorgio Mondini shared an EJ15B.

The Portuguese driver kicked off the team's second test with a program that included set-up work, tyre testing and control system evaluations. We made considerable progress in these areas and will continue exploring these areas with Christijan Albers tomorrow.

Today's session was intended as a familiarisation for Winkelhock and a chance to complete more mileage with the team following his test at the end of 2005 in Jerez. Mondini ran a limited number of laps in preparation for a full day of testing tomorrow.