Rubens Barrichello led a Honda Racing 1-2 on the final, rain-hit day of testing this week at Jerez in Spain.
The Brazilian just edged out his teammate James Rossiter by one tenth of a second as the pair continued to focus on set-up work and evaluation of the new 2007 Bridgestone rubber.
A major downpour in the morning meant that meaningful laps could not be done until just before lunchtime, although Rossiter still managed to complete 108 laps over the course of the day.
Lewis Hamilton, who had been quickest overall on Thursday, was third fastest - just two-tenths behind Rossiter - but his day was marred when he brought out the red flag in the final hour, when his car stopped on track.
Ralf Schumacher continued to focus on adapting the Toyota TF106B chassis to the Bridgestone tyres, having felt that more work was needed at Jerez than had been required at Barcelona last week.
Behind Pedro de la Rosa, Heikki Kovalainen was sixth fastest for Renault despite suffering an engine failure at 1:00pm. The Finn was less than two hundredths of a second faster than teammate Giancarlo Fisichella.
Nick Heidfeld was eighth overall, as his team continued to work on finding a good set-up for the Bridgestone tyres.
Anthony Davidson was ninth quickest, ahead of Timo Glock in the BMW-Sauber and Kamui Kobayashi in the Toyota.
It was a bad day for Ferrari, who saw both Felipe Massa and Luca Badoer stop on the track. The pair ended the day well down the order.
The other red flag of the day was caused when Kazuki Nakajima in the Williams suffered an engine failure at 3:20pm.
Pos Driver Team Time Laps 1. Barrichello Honda (B) 1:20.008 65 2. Rossiter Honda (B) 1:20.171 108 3. Hamilton McLaren-Mercedes (B) 1:20.325 79 4. R.Schumacher Toyota (B) 1:20.339 61 5. de la Rosa McLaren-Mercedes (B) 1:20.342 84 6. Kovalainen Renault (B) 1:20.372 70 7. Fisichella Renault (B) 1:20.390 88 8. Heidfeld BMW-Sauber (B) 1:20.436 110 9. Davidson Super Aguri-Honda (B) 1:20.542 87 10. Glock BMW-Sauber (B) 1:20.785 105 11. Kobayashi Toyota (B) 1:20.978 70 12. Webber Red Bull-Ferrari (B) 1:20.985 79 13. Massa Ferrari (B) 1:21.143 46 14. Coulthard Red Bull-Ferrari (B) 1:21.325 63 15. Badoer Ferrari (B) 1:21.327 43 16. Speed Toro Rosso-Cosworth (B) 1:21.327 51 17. Nakajima Williams-Toyota (B) 1:23.600 16 All timing unofficial