Kamui Kobayashi topped the timing sheets during testing on Friday morning, two tenths ahead of Pastor Maldonado in the Williams and almost a second clear of Jenson Button's McLaren.
Although lap times from pre-season test sessions are rarely a sign of true pace, the strong performance from mid-table teams like Sauber and Williams goes to show that they have had a successful winter development programme.
Kobayashi of Japan posted a time of 1m 22.312 - the fastest time yet this week, with Maldonado and Button two tenths and nine tenths behind him respectively - the Sauber driver's time is around six tenths away from the lap record for Catalunya, which was set by Kimi Raikkonen in 2008 and stands at 1m 21.670.
Jenson Button set his fastest laptime early in the session on the hard tyres, while Kobayashi was using Pirelli's super soft compound, which is much quicker than the medium and harder tyres.
Friday is the last day of testing for a week so many of the teams opted to run for long stints in an attempt to simulate race distances of around 300km to stress-test key componants.
Nico Rosberg drove his Mercedes for 92 laps in the four-hour session, equating to almost a race and a half in distance, while Maldonado posted 86 timed laps and Kobayashy recorded 63.
Further down the standings, Paul di Resta completed 45 laps, while Kovalainen posted just 16 due an electrical fault forcing the team to change the Caterham's engine.
Di Resta's morning was hampered as he understeered off into the gravel at Campsa corner. The incident brought out the red flags, stopping the session for a few minutes while the Scot's car was recovered to the pits.