Nick Heidfeld set the pace for BMW Sauber at Jerez on Tuesday as the final four-day test session of the year got underway.

Heidfeld, who will be in action every day this week except on Friday, completed 78 laps in total - his best a 1 minute 19.042 seconds, which around a tenth up on Jenson Button, who was 'best of the rest' for Honda.

Both Heidfeld and Button though were using Bridgestone's new development specification tyres, ahead of the possible re-introduction of slicks in 2009.

Heidfeld was joined in the sister F1.07 by 2007 British F3 champion, Marko Asmer and GP2 race winner, Javier Villa. Villa ran in the morning and did 53 laps in total, while Asmer took over the car this afternoon and also did around 50 laps. Robert Kubica will take over that chassis on Tuesday, when he joins Heidfeld to continue work on mechanical and aero developments.

Button meanwhile was second, notching up 70 laps in total, with ex-Ferrari man, Ross Brawn watching from the sidelines after starting work as Honda team principal last week.

Pedro de la Rosa completed the top three for McLaren, albeit more than five tenths off the pace, although admittedly on grooved rubber.

McLaren ran two cars on Tuesday, one set-up to focus on aerodynamic development and the other on the proving of chassis components. de la Rosa and fellow McLaren tester, Gary Paffett, who ended the day in P7 on the timesheets, swapped between the two cars during the day.

Paffett will be replaced by Lewis Hamilton on Wednesday and Thursday, before getting back behind the wheel on Friday, when the team plan to run with the slick Bridgestone tyres.

Further down the order, 2007 champion, Kimi Raikkonen was fourth, on his first outing with the Scuderia since the season ending Brazilian Grand Prix. The Finn was working on 'the development of new components, with special emphasise on electronics'.

Marc Gene was out in the sister car and he managed 67 laps in total, 11 less than Kimi. Gene will hand over his F2007 to Felipe Massa on Wednesday.