Buemi on top at Jerez again

Continuing to fill in for Mark Webber at Red Bull Racing, Buemi edged out his teammate Sebastian Vettel by three tenths of a second - with Vettel having a few off-track moments at Turn One.

Speaking about his day, Buemi said: "It's been a very good test so far, we've been improving with every lap, which is really good for next season and I'm happy. We're learning more about the slick tyres too, which is important. I'm looking forward to tomorrow and trying to improve myself more."

Nick Heidfeld was third quickest for BMW Sauber, using the standard F1.08 to work through mechanical setup evaluation of the car, as well as gathering slick tyre data.

"After the delay in the morning the weather was nearly perfect, so overall it was a good day for me," said Heidfeld.

"I did short as well as long runs to compare tyre wear. At the end of the session I did some race start simulations, as this is also an area where we have to adjust to the slick tyres."

Teammate Robert Kubica showed how advanced BMW Sauber were with their KERS development as he focused on strategies for using the device.

Kazuki Nakajima was the only other driver testing, completed a total of 105 laps as he continued 2009 work for Williams.

Today's times:

Pos  Driver     Team                  Time     Laps
 1.  Buemi      Red Bull-Renault (B)  1:17.029  83
 2.  Vettel     Red Bull-Renault (B)  1:17.319  83
 3.  Heidfeld   BMW Sauber       (B)  1:19.303  85
 4.  Kubica     BMW Sauber       (B)  1:20.006  61
 5.  Nakajima   Williams-Toyota  (B)  1:20.332 105