Kamui Kobayashi ensured that Sauber ended the first of two pre-season tests at Catalunya on a high with the best time on day four of running at the Spanish circuit.
Using the softer compound of Pirelli tyre, the Japanese driver jumped to the top of the times during the morning session and remained unbeaten all afternoon as teams followed the same pattern as on the previous three days of running – focusing on longer stints on track and race simulation work during the afternoon.
Kobayashi's best time of 1min 22.312secs was the quickest seen in Barcelona this week and good enough to beat the Williams of Pastor Maldonado by two-tenths of a second. The pair were also the busiest drivers in action, with both completing more than 130 laps as the second pre-season test of the year drew to a close.
Paul di Resta was one person to improve during the afternoon to take third place for Force India, having earlier caused a red flag in the morning session when he suffered a trip into the gravel.
The Scot was less than a tenth of a second ahead of Jenson Button's McLaren, with Felipe Massa taking fifth for Ferrari.
Mark Webber and Jean-Eric Vergne were sixth and seventh for Red Bull and Toro Rosso respectively, with neither driver breaking the 100 lap marker over the course of the day. The opposite was true for Nico Rosberg however as he was wracked up another 139 laps in the new Mercedes to end the day eighth; putting the car through another race simulation in the process.
An engine change meant Heikki Kovalainen completed the fewest number of laps for Caterham, although the Finn was still able to put 70 laps on the board – albeit well down on the rest of the field.
Marussia meanwhile was forced to abandon its planned programme after a suspension issue left Charles Pic in the garage for the day.