Pastor Maldonado finished top of the timing sheets at the end of morning practice on the third day of pre-season testing at Catalunya, almost one second ahead of second place Schumacher.
The Williams driver posted a time of 1m 22.391 and completed 52 laps during the four-hour session at the Barcelona circuit, with the seven-time World Champion Michael Schumacher posting a time of 1m 23.384 having completed 54 laps.
Lap times posted during testing never provide an entirely accurate picture of overall pace, but Maldonado's time goes to show that his Williams is at least on par with the other cars, after the team had its worst ever season in 2011.
In a session that saw many red flags - most noticeably when the engine cover of Paul Di Resta's Force India car came off - Kobayashi came third in the Sauber after recording 59 laps.
The 2009 World Champion Jenson Button posted the forth fastest time of the morning, with a 1m 23.918 and completed 39 flying laps.
Formula One newcomer Jean Eric-Vergne posted a time of 1m 24.433 in his Torro Rosso placing him in fifth place, two tenths ahead of Felipe Massa in the Ferrari F2012.
Mark Webber recorded a time of 1m 24.835 which put him in seventh place; Glock in the Marussia (formerly Virgin Racing), Petrov in the Caterham and Di Resta in the Force India round out the top ten.
The morning session was brought to a close three minutes early after a red flag was issued due to Kobayashi parking his Williams out on track - the team claim that he ran out of petrol.
The unofficial timing - as reported by AutoSport - for the morning session of 23 February are as follows: