Toro Rosso has picked up where it left off in Barcelona last month, though once again, little can be read into the times as teams continue to run various systems and devices, some to the 2008 regulations, some to 2009. The day was neatly divided in two by the weather, which was dry at first, before rain affected the afternoon running.

Nonetheless, it was the Sebastiens - Buemi and Bourdais - who led the way as the penultimate test of 2008 got underway. Both cars went out on track in the same configuration as at the previous Barcelona test, with downforce levels replicating those expected from the new aero rules for next year. Tyres were also the same 'soft' slicks.

Both drivers concentrated on set-up work, with Buemi additionally assessing various aero options. The rain saw a switch to wet weather tyres, with the two drivers running a comparison between this year's rain tyre and a development tyre for 2010. Buemi will be driving for the remaining two days, with Bourdais running again tomorrow morning, before handing over to Takuma Sato for the final day and a half.

Due to the damp conditions, McLaren opted to limit its mileage in the morning and towards the end of the day, when a mid-afternoon shower rendered the track too damp for meaningful running. Pedro de la Rosa concentrated on set-up work in an MP4-23A while Gary Paffett evaluated KERS boost levels in a 23K.

Tomorrow's programme sees Heikki Kovalainen return to the cockpit for the first time since Brazil, getting his first taste of KERS in the MP4-23K. De la Rosa will focus on aero work in a more heavily 2009-modified 23A.

Kimi Raikkonen was on duty for Ferrari, returning to the cockpit after a break of exactly one month; the last time he'd driven dating back to the World Finals at Mugello on 9th November. The Finn worked mainly on finding the best set-up on the car and began a long run test for the engine, which will go on for the entire test. Tomorrow, Felipe Massa will join the 2007 World Champion.

Due to the conditions, BMW did not start testing until around 11.00. Nick Heidfeld and Christian Klien ran two F1.08B interim cars featuring a modified 2008 chassis with some of the bodywork complying to the 2009 regulations. Only Klien's car was fitted with BMW's own KERS device. His test schedule was curtailed by a precautionary engine change. The Austrian stopped on track when sensors indicated a mechanical problem.

Heidfeld concentrated on set-up work with the suspension as well as the new aero package. Although the session came to a premature end when it started to rain again at around 15.00, he collected valuable data with the F1.08B running on 2009 slick tyres.

"Based on the results of the last test in Barcelona we changed the mechanical setup of the car," said the German. "It looks like we are moving in the right direction."

Kazuki Nakajima was on duty for Williams, taking over from Dani Clos who got the Jerez session underway yesterday.

"The heavy rain showers interrupted the majority of today's session so we spent much of the time in the garage," said Test Team Manager, Dickie Stanford. "During the time we did get on track, Kazuki ran through set-up configurations on the FW30B and testing the slick tyres. Nico (Rosberg) joins us for the last two days of the test and will continue work on our development programme."