Michael Schumacher started with a spin then set the fastest lap after opting for an early return to F1 testing.
Schumacher is raring to go ahead of the 2006 season
Germany's seven-time world champion was back behind the wheel for Ferrari at the Jerez circuit in Spain.
Thursday's outing was the first time since 1998 that Schumacher has tested between the end of the season in October and the new year.
"I feel very fresh, very motivated," he said as he began his bid to put a poor 2005 season behind him.
Schumacher did 68 laps with a best time of one minute 18.958 seconds, quicker than Brazilian team mate Felipe Massa in a V10-powered F2005 car.
The Renault duo of Franck Montagny and Heikki Kovalainen were third and fourth respectively.
F1's engine rules are changing next year, with a switch from three litre V10 to 2.4 litre V8 units, and teams are testing with both.
Schumacher said last weekend that he wanted to get back in the car because he felt he did not deserve his usual winter break.
He won only once in 2005, the six-car US Grand Prix fiasco at Indianapolis, and was dethroned after a five-year reign by Renault's Spaniard Fernando Alonso.
Britain's Anthony Davidson, who has yet to decide whether to stay as Honda test driver or take up a race seat with Super Aguri, was fifth fastest in Jerez.
His Honda colleague Adam Carroll was eighth.