Heidfeld quickest on slicks at Jerez

Button was the first to use one of the set of evaluation slick tyres early in the day on his Honda to head the times, before Heidfeld bettered his effort later on in his BMW-Sauber.

But despite predictions that slick tyres could slash laptimes by around two seconds, Heidfeld's best effort was only six tenths of a second faster than McLaren's Pedro de la Rosa on grooved tyres.

Kimi Raikkonen marked his return to the Formula One cockpit since winning the world championship in Brazil with the fourth best time for Ferrari, ahead of Nelson Piquet Jr. in the Renault and Sebastien Bourdais in the Scuderia Toro Rosso.

McLaren test driver Gary Paffett was seventh quickest, with Mark Webber eighth for Red Bull Racing and Marc Gene ninth for Ferrari.

Honda test driver Mike Conway completed more mileage for Super Aguri, with teammate James Rossiter the only other driver to run slicks setting the 12th best time.

Timo Glock, having the first run for his new Toyota team was 13th fastest, just ahead of Giancarlo Fisichella in the Force India. The Italian's day had got off to a disappointing start when he spun early on, but luckily he did not cause any damage to the car. A differential problem late in the day also meant a late try out on slick tyres was inconclusive.

Despite that, Fisichella was pleased with his first impression of Force India.

"It's my first day back in the car nearly two months after the last race in Brazil, plus my first with another car and new engine, and of course without the electronics," he said. "Considering this I am quite happy about how the day went though.

"We did have a couple of issues so I didn't run as much as I would have liked; with new tyres I had a problem with the hydraulic pressure, and when I tried out the slick tyres there was a problem on the diff so we didn't get a proper idea of how the tyres will work. All the same I do think it's been a positive day though and a good basis for tomorrow."

Nico Hulkenberg completed his first day of Formula One action for Williams as he chases a test driver deal with the team, while Marko Asmer boosted his chances of landing the BMW Sauber test deal by setting a time 1.6 seconds quicker than Javier Villa.

Kamui Kobayashi returned to Formula One action with the Toyota team, completing the most number of laps during the day with 111.

"It was great to get back in a Formula One car again," said Kobayashi. "Even though I don't officially become third driver until January, it feels like I have already begun my role and today I was able to learn a lot about the car.

"At the start of the day I was just trying to get comfortable with the car and the track and I was able to do a lot of laps which really helped me. In the afternoon I could work more on set-up and understanding the development parts on the car and I think we made some good progress.

"I enjoy working with the team and this test is great experience for me before I officially start as third driver next year. Now I can't wait to get back in the car tomorrow."

Today's times:

Pos  Driver        Team                      Time      Laps
 1.  Heidfeld      BMW-Sauber           (B)  1:19.042   73
 2.  Button        Honda                (B)  1:19.155   65
 3.  de la Rosa    McLaren-Mercedes     (B)  1:19.712   48
 4.  Raikkonen     Ferrari              (B)  1:20.083   73
 5.  Piquet        Renault              (B)  1:20.366   66
 6.  Bourdais      Toro Rosso-Ferrari   (B)  1:20.615   97
 7.  Paffett       McLaren-Mercedes     (B)  1:20.638   50
 8.  Webber        Red Bull-Renault     (B)  1:20.682   65
 9.  Gene          Ferrari              (B)  1:20.832   67
10.  Conway        Super Aguri-Honda    (B)  1:20.927   87
11.  Vettel        Toro Rosso-Ferrari   (B)  1:21.086   45
12.  Rossiter      Super Aguri-Honda    (B)  1:21.246   71
13.  Glock         Toyota               (B)  1:21.336   69
14.  Fisichella    Force India-Ferrari  (B)  1:21.424   41
15.  Hulkenberg    Williams-Toyota      (B)  1:21.556   28
16.  Montagny      Force India-Ferrari  (B)  1:21.559   65
17.  Nakajima      Williams-Toyota      (B)  1:21.586   33
18.  Asmer         BMW-Sauber           (B)  1:21.962   57
19.  Kobayashi     Toyota               (B)  1:22.186  111
20.  Villa         BMW-Sauber           (B)  1:23.583   53

All Timing Unofficial