While high winds and rain were disrupting BMW's test at Valencia, almost continual light rain was causing problems at Jerez, where the first major test of 2008 was brought to a close.

Topping the timesheets at the end of the day was GP2 Series Champion Timo Glock, who was getting his first taste of the TF108.

The German's task was to gain as much track time as possible with the new car while also comparing set-up changes and mechanical settings. Kamui Kobayashi was in the TF107 for its final planned official test but rain in the morning led him to sit out the first two hours.

With a new car to test, Glock was immediately down to work on the wet track and he made good progress on a lengthy programme before a spin into the gravel just before lunch. No damage was done and after the TF108 was cleaned and checked he resumed, with Kobayashi now on track looking into set-up and fine-tuning the new gearbox and ECU.

Another trouble-free run from TF108 saw Glock end the day on 96 laps, meaning the new car has clocked up an impressive total of over 1,500km over four days. The team will be in action again in Valencia next week when two TF108s are expected to be tested.

"I am pleased with our progress today," said Glock, "and I believe we have made some significant improvements to the new car. It is encouraging to see us end the day with the fastest lap and I think we made a step forward. Once again the car was extremely reliable and that allowed us to complete a lot of laps and gather plenty of information. This is a completely different car compared to the TF107 but it is a good step forward and we know what we need to work on to improve. I made a small mistake in the morning on the damp track when the rear wheels locked and I spun but it didn't cost us much time. The team worked really hard this week to improve the car and I am happy."

"The rain in the morning meant there was not much point in me going out, because it is not possible to make accurate set-up judgements in such conditions," said Kobayashi. "So I waited and when the track began to dry I was able to start my programme. Overall it went well and we have had a positive test. I think we have learned some things during my two days and now I am looking forward to getting the chance to drive the TF108 in the coming tests. Both Timo and Jarno have been pretty positive about it so I can't wait."

"We have had a very productive four days here with the new car," added Test Team Manager, Gerd Pfeiffe, "including the roll-out. It has been a promising start to the year and we have made good progress understanding the TF108. But this is only the first step and we know we have more work to do in the next five pre-season tests to improve the car's performance. Today was another busy day for Timo with the new car and he has conducted some important set-up work, including an impressive lap in the afternoon. Kamui did fewer laps because of the damp conditions but he completed the programme we had planned for him."

Despite two offs, one in the morning and another in the afternoon, Lewis Hamilton finished the day second quickest. The conditions meant that, on top of the continuing development programme, the team took the opportunity to look into improving engine drivability and car handling with wet settings. In addition the MP4-23 has been running with the new FIA ECU codes and development of this was also a focus. Hamilton was partnered by Heikki Kovalainen, who ended the day sixth quickest.