Force India's Adrian Sutil lapped quickest in free practice for the Italian Grand Prix on Friday while former team-mate Giancarlo Fisichella was slowest on his first day as a Ferrari driver.
Sutil, who has yet to score a point this season, lapped the Monza circuit in one minute 23.924 seconds after being third quickest in the morning.
French rookie Romain Grosjean was second in a Renault.
McLaren duo Lewis Hamilton and Heikki Kovalainen topped a sunny first session, with the world champion setting a best time of 1:23.936.
Fisichella, who put Force India on pole at the Belgian Grand Prix and finished second for the team's first points, had a mixed debut with the Maranello team he has always longed to drive for.
The experienced Roman was eighth quickest, two places ahead of 2007 world champion and team-mate Kimi Raikkonen, although he had switched to the softer and quicker tyres for the late run that produced the best time.
Before then, he had been among the last on the timing screens and he returned to the bottom of the list in the afternoon.
Fisichella has replaced struggling compatriot Luca Badoer, himself a stand-in for injured Brazilian Felipe Massa, at Ferrari.
Championship leader Jenson Button, who has scored just 11 points in his last five races after winning six of the first seven, was seventh fastest for Brawn in the morning but then finished 19th.
Button leads Brazilian team-mate Rubens Barrichello by 16 points with five races remaining.
Italian Vitantonio Liuzzi, replacing Fisichella at Force India, managed the 12th best time in the afternoon on his return to a full Formula One race seat for the first time since 2007.