Barcelona - Finnish driver Kimi Raikkonen smashed team-mate Sebastian Vettel's best time in pre-season testing by nearly half a second to dominate the morning session of the final day of testing on Friday.
Raikkonen edged to within three tenths of the track record in 1:18.634 to register the fastest time of the day by nearly a second.
Vettel's best of 1:19.024 on Thursday had already raised hopes that Ferrari, who haven't won a drivers' championship since Raikkonen's success in 2007, can bring an end to Mercedes' three years of dominance.
Three-time world champion Lewis Hamilton claimed Ferrari were "bluffing" with their eye-catching testing times and Mercedes may be keeping their powder dry for the first Grand Prix of the year in Melbourne on March 26.
Valtteri Bottas was well over a second back on Raikkonen in fourth on the same supersoft tyre compound.
Hamilton will take over from Bottas for the afternoon session.
Dutch wonderkid Max Verstappen was second fastest as Red Bull again showed that they look set to be the third force behind Mercedes and Ferrari this season.
Fernando Alonso and McLaren's misery continued, though, as the two-time world champion broke down with the same electrical problems that saw Stoffel Vandoorne stop twice on Thursday.
Alonso eventually got 19 laps under his belt but was once again relegated to last among the 10 drivers in action on the timesheets.