Kimi Raikkonen put Ferrari back on top of the times on Thursday as the first of two pre-season Barcelona Formula 1 tests came to an end.
The Finn used the ultrasoft tyres late in the morning session to post a best time of 1:23.477, finishing the day over eight tenths clear of Red Bull's Daniil Kvyat.
The Russian, also using the ultrasofts for his best lap, managed over 90 laps in the RB12 to outpace Alfonso Celis, who completed another promising showing for Force India.
Celis set his fastest time on supersofts.
Renault had its more productive outing yet with Kevin Magnussen behind the wheel, the Dane emerging as the busiest man on track with 153 laps completed on his way to the fourth fastest time of the session.
Magnussen was the quickest of the drivers not running ultrasofts or supersofts, his best time set with softs, although he caused a late red flag when his car stopped at Turn 3 with 15 minutes to go.
Max Verstappen was fastest of those on medium tyres, the Toro Rosso racer also going over the 100-lap mark to complete the top five.
Felipe Nasr finished sixth in the 2015 Sauber, ahead of Mercedes' Nico Rosberg, who drove the car in the afternoon, taking over from Lewis Hamilton.
The German squad's unprecedented reliability was again on display, the duo covering 185 laps between them.
Mercedes has covered 229 laps more than last year in the four days of the test at the Spanish track.
Haas wrapped up its first ever Formula 1 test with another solid outing, Esteban Gutierrez completing 89 laps before his car stopped on track with a problem one hour from the end.
Manor's Rio Haryanto continued the team's programme for the second day running, but his session came to an early finish after he crashed 90 minutes into the afternoon session.
The Indonesian, the only driver to have spun or crashed during the test, lost control of his car at Turn 5 and ended up making contact with the wall.
Fernando Alonso, meanwhile, had a disastrous day and became the first driver to fail to set a time in a session since the test started on Monday.
The McLaren driver, on his second day at the wheel of the MP4-31, managed just three untimed laps early in the morning before a coolant leak prevented him from completing any more running.
Day 4, final testing times:
|2||D. Kvyat||Red Bull||1:24.293||96|
|3||A. Celis Jr||Force India||1:24.640||75|
|5||M. Verstappen||Toro Rosso||1:25.393||110|
|12||F. Alonso||McLaren||no time||3|