Second overall was McLaren test driver Pedro de la Rosa, whose car was fitted with a 2008-spec front wing due to the rainy conditions (for improved stability). The Spaniard completed his second test with the MP4-24 car, after previously concluding another on-track test of McLaren's 2009 challenger last week.
Third overall was Williams F1's test driver Nico Hulkenberg, who completed 28 laps with the new FW31 car for a best time of 1:46.335. The German rookie – in his first season as test driver for Frank Williams' team – was followed by Renault's Nelsinho Piquet, who concluded his first test on the new R29 car. Kamui Kobayashi finished on the bottom of the timing sheets, ending the day more than 2 seconds behind Piquet.
The final two hours of the testing session at Portimao were affected by rain, therefore allowing little action from all teams present at the Portuguese track.
Ferrari, who have pulled out from the Portimao group test due to bad weather forecast, encountered the exact same problems back in Italy, at Mugello. Heavy rain affected the Scuderia's first proper test on the F60 machinery, with Finland's Kimi Raikkonen completing a total of 54 laps for a best time of 1:34.430.
Here are the complete results of yesterday's testing at Portimao:
1. Sebastien Buemi (Toro Rosso-Ferrari) 1:41.528
2. Pedro de la Rosa (McLaren-Mercedes) 1:46.076
3. Nico Hulkenberg (Williams-Toyota) 1:46.335
4. Nelsinho Piquet (Renault) 1:48.907
5. Kamui Kobayashi (Toyota) 1:50.989