Button on top again at Barcelona

Button, testing with this year's 007 car with a V10 engine, set a quickest time of 1:14.145.

He finished ahead of teammate Anthony Davidson, who continued working the hybrid BAR chassis powered by the new Honda V8 engine for much of the day before getting his hands on the 2005 car late in the day to set his best time.

That was when Button got to try out a Honda V8 for himself for the first time - and he reported to the team that the new power-units were not as bad as he thought and produced less vibration than expected.

Toyota's test driver Ricardo Zonta posted the third quickest time in the team's new TF106, which today was also driven for the first time by  Ralf Schumacher, who took over from teammate Jarno Trulli.

The German, however, could not escape trouble. His car suffered a spectacular engine failure just before lunchtime that left parts of the Toyota V8 scattered all over the track. Even so, Schumacher managed 48 laps on his way to the ninth fastest time.

The Williams team enjoyed a better session today after finishing at the bottom of the times on Wednesday, Australian Mark Webber posting the fourth quickest time in the Cosworth-powered FW27. Teammate Nico Rosberg was eighth fastest.

McLaren were back to work after skipping yesterday's session, working with Pedro de la Rosa and Juan Pablo Montoya, who was back behind the wheel of his car after the end of the 2005 season. The Colombian missed almost three hours of action, however, with a mechanical problem.

World Champions Renault had three drivers in action as World Series champion Robert Kubica and Former Formula Renault Eurocup V6 champion Giorgio Mondini made their debut at the wheel of a Grand Prix car.

Frenchman Franck Montagny was also working for the team at Barcelona.

American driver Scott Speed replaced Vitantonio Liuzzi at the Toro Rosso team, who continued testing with last season's Red Bull's car powered by a restricted V10 engine.

Today's times:

Pos  Driver        Team                Tyres  Time     Laps
 1.  Button        BAR-Honda            (M)  1:14.145   94
 2.  Davidson      BAR-Honda            (M)  1:15.273   78
 3.  Zonta         Toyota               (B)  1:16.647   60
 4.  Webber        Williams-Cosworth    (B)  1:17.282   66
 5.  de la Rosa    McLaren-Mercedes     (M)  1:17.449   79
 6.  Montagny      Renault              (M)  1:17.592   86
 7.  Montoya       McLaren-Mercedes     (M)  1:17.763   61
 8.  Rosberg       Williams-Cosworth    (B)  1:17.805   44
 9.  R.Schumacher  Toyota               (B)  1:17.982   48
10.  Kubica        Renault              (M)  1:17.997   41
11.  Coulthard     Red Bull-Cosworth    (M)  1:18.318   85
12.  Speed         Toro Rosso-Cosworth  (M)  1:19.053   82
13.  Mondini       Renault              (M)  1:19.093   40
14.  Doornbos      Red Bull-Cosworth    (M)  1:19.114  110

All Timing Unofficial