Jenson Button put the Brawn GP team back on top of the timesheets at Jerez, as the Brackley-based team completed its preparations for the start of the season in Australia.
Button's best lap of 1:17.844 was half a second quicker than the best time of the week set by Renault's Fernando Alonso yesterday.
The Briton, however, was closely followed by Williams driver Nico Rosberg, who finished less than two tenths behind in the Toyota-powered FW31.
Nelson Piquet was third quickest for Renault, the Brazilian matching the pace set by team-mate Fernando Alonso yesterday.
"My final day of testing went really well and I'm pleased that we were able to do so many laps," said Piquet. "We were looking at the car's aero performance today as well as doing some set-up work in preparation for the first race and overall we found a good balance with the car.
"It was pretty windy, but the track conditions were good so we were able to get a lot done. I'm now ready for the season to start next week and I think as a team we can be happy with the work we've done over the winter."
Lewis Hamilton continued with McLaren's low-key testing, posting the slowest time of the day.
The test continues tomorrow, but only with McLaren and Williams on track.
Pos Driver Team Time Laps
1. Button Brawn-Mercedes (B) 1:17.844 114
2. Rosberg Williams-Toyota (B) 1:18.071 66
3. Piquet Renault (B) 1:18.382 128
4. Hamilton McLaren-Mercedes (B) 1:19.121 118