Pastor Maldonado's late morning run was enough to keep Williams at the top of the timesheets as the third and penultimate day of pre-season testing in Barcelona drew to a close.
Long runs were once again the order of the day in the afternoon, with Michael Schumacher delivering the most extensive - a 59-lap stint on only the third public day of testing for Mercedes's W03.
Vitaly Petrov was the only driver to improve upon is morning benchmark, as a switch to Pirelli's super soft rubber yielded a 1m26.448s in the final 15 minutes. He stayed tenth however, just over four seconds down on Maldonado.
The Venezuelan likewise set his best time - the fastest seen so far in Barcelona - on the red super soft compound, lapping the circuit in 1m22.391s in the more advantageous morning conditions.
Schumacher's afternoon work took him to 127 laps for the day, the most by any driver. He ended second fastest as a result of his morning pace, just over nine tenths down on Maldonado.
Kamui Kobayashi was next up for Sauber, completing 99 laps in the C31.
Jenson Button was the last driver to dip under the 1m24s bracket in the morning, while in the afternoon he managed a total of 74 laps - often in individual stints of around ten laps, punctuated by short stops in the garage.
Jean-Eric Vergne finished fifth for Toro Rosso, ahead of Mark Webber in the Red Bull and Felipe Massa in the Ferrari - the latter pair sharing the exact same time of 1m24.771s.
Massa brought the day to a slightly premature halt when he stopped on the exit of the pitlane two minutes from the end. Mark Webber had earlier stopped out on track at Turn 8, one of several short red flag interludes.
Paul di Resta, taking over from yesterday's pacesetter Nico Hulkenberg at Force India, set the eighth fastest time, ahead of Timo Glock in the 2011-spec Marussia.
Despite his afternoon improvement Vitaly Petrov rounded out the day's runners in the Caterham CT 01.
Pos Driver Team Time Laps
1. Maldonado Williams 1m22.391s 106
2. Schumacher Mercedes 1m23.384s +0.993 127
3. Kobayashi Sauber 1m23.582s +1.191 99
4. Button McLaren 1m23.918s +1.527 114
5. Vergne Toro Rosso 1m24.433s +2.042 78
6. Webber Red Bull 1m24.771s +2.380 97
7. Massa Ferrari 1m24.771s +2.380 84
8. Di Resta Force India 1m25.646s +3.255 83
9. Glock Marussia 1m26.173s +3.782 108
10. Petrov Caterham 1m26.448s +4.057 70
All timing unofficial