Double R Racing's Louis Foster set the fastest time in the third test session of the day at Oulton Park, with his effort of 1m32.567s being over six tenths of a second clear of Douglas Motorsport's Manaf Hijjawi.
A red flag with five minutes remaining prevented drivers from setting as many laps as in previous sessions, with Foster managing a total of seven in the 25 minute session.
Foster's teammate Benjamin Pedersen was third quickest, just 0.021s behind Hijjawi and 0.018s clear of Carlin's Nazim Azman, with Lanan's Bart Horsten 0.013s further back.
Douglas Motorsport's Kiern Jewiss was sixth fastest, 0.033s clear of teammate Ulysse De Pauw, with Chris Dittmann Racing's Josh Skelton in eighth, 0.072s behind.
Hillspeed duo Oliver Clarke and Sasakorn Chaimongkol completed the top-10 in a session that saw ambient temperatures hit over 30 degrees celsius.
Chris Dittmann Racing's Nico Varrone was just outside the top-10, and over a tenth clear of Lanan's Piers Prior, who in turn was a couple of tenths faster than teammate Josh Mason.
Hitech duo Reece Ushijima and Kush Maini were 14th and 15th, with overall pacesetter Maini failing to complete a representative lap time, while Carlin's Kaylen Frederick only completed one lap before bringing out a brief red flag.
The session resumed with five minutes still remaining, though only De Pauw, Skelton and Varrone ventured out on track.
The final session of the day starts at 16.20 UK time, with live timing available by clicking here.
BRDC British F3 Championship, Oulton Park, Friday test session three result:
1. Louis Foster, Double R Racing, 1m32.567s
2. Manaf Hijjawi, Douglas Motorsport, +0.664s
3. Benjamin Pedersen, Double R Racing, +0.685s
4. Nazim Azman, Carlin, +0.703s
5. Bart Horsten, Lanan Racing, +0.716s
6. Kiern Jewiss, Douglas Motorsport, +0.765s
7. Ulysse De Pauw, Douglas Motorsport, +0.798s
8. Josh Skelton, Chris Dittmann Racing, +0.870s
9. Oliver Clarke, Hillspeed, +0.975s
10. Sasakorn Chaimongkol, Hillspeed, +1.025s
11. Nico Varrone, Chris Dittmann Racing, +1.086s
12. Piers Prior, Lanan Racing, +1.226s
13. Josh Mason, Lanan Racing, +1.423s
14. Reece Ushijima, Hitech GP, +2.917s
15. Kush Maini, Hitech GP, +7.196s
16. Kaylen Frederick, Carlin, no time set
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