Elite Motorsport's Alex Kattoulas set the fastest time in the second and final test session of the day at Oulton Park, but Dan Guinchard's time from session one remained unbeaten.
Japanese-Greek contender Kattoulas set a 1m34.517s, falling just short of Guinchard's morning benchmark of 1m34.447s, though session two was twice interrupted in the second half, with red flags brought out by separate incidents for Josh McLean and Thomas Ingram Hill.
Kattoulas was 0.151s clear of teammate Isaac Phelps with KMR Sport's Alex O'Grady third for the second successive session.
Hillspeed's Guinchard had to settle for fourth in session two, the first time in five sessions he's not been on top of the times.
Graham Brunton Racing's Mayer Deonarine and Elite's Ary Bansal, making his first on track appearance of the week, completing the top-six.
Douglas Motorsport's Dayton Coulthard was 0.040s further back in seventh, and one hundredth of a second clear of Arden's Leon Wilson.
Graham Brunton Racing's Alex Berg and the second Douglas car of Luke Hilton completed the session two top-10.
Just 0.070s separated Guinchard and Kattoulas at the top of the combined times. Like Kattoulas, Phelps and O'Grady each set their best laps in session two and were third and fourth quickest on Friday.
Douglas Motorsport's Enzo Hallman was fifth fastest thanks to his session one effort, with Wilson sixth, also with his session one time.
Graham Brunton Racing's Callum Baxter was seventh ahead of teammate Deonarine, with Bansal and Hilton completing the day's top-10, which was covered by just over three quarters of a second.
The GB4 field return to action with qualifying tomorrow (Saturday) at 13.05.
GB4 Championship, partnered by the BRDC, Oulton Park Friday session two top-10 result:
1. Alex Kattoulas, Elite Motorsport, 1m34.517s
2. Isaac Phelps, Elite Motorsport, +0.151s
3. Alex O'Grady, KMR Sport, +0.344s
4. Dan Guinchard, Hillspeed, +0.435s
5. Mayer Deonarine, Graham Brunton Racing, +0.641s
6. Ary Bansal, Elite Motorsport, +0.691s
7. Dayton Coulthard, Douglas Motorsport, +0.731s
8. Leon Wilson, Arden Motorsport, +0.741s
9. Alex Berg, Graham Brunton Racing, +1.017s
10. Luke Hilton, Douglas Motorsport, +1.051s
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GB4 Championship, partnered by the BRDC, Oulton Park Friday combined result:
1. Dan Guinchard, Hillspeed, 1m34.447s
2. Alex Kattoulas, Elite Motorsport, +0.070s
3. Isaac Phelps, Elite Motorsport, +0.221s
4. Alex O'Grady, KMR Sport, +0.414s
5. Enzo Hallman, Douglas Motorsport, +0.604s
6. Leon Wilson, Arden Motorsport, +0.648s
7. Callum Baxter, Graham Brunton Racing, +0.693s
8. Mayer Deonarine, Graham Brunton Racing, +0.711s
9. Ary Bansal, Elite Motorsport, +0.761s
10. Luke Hilton, Douglas Motorsport, +0.774s
11. Dayton Coulthard, Douglas Motorsport, +0.801s
12. Tom Mills, KMR Sport, +0.868s
13. Alex Berg, Graham Brunton Racing, +0.909s
14. Leandro Juncos, Hillspeed, +1.131s
15. Stefan Bostandjiev, Pace Performance, +1.199s
16. Jack Taylor, Fortec Motorsports, +1.221s
17. Ava Dobson, Arden Motorsport, +1.267s
18. Thomas Ingram Hill, Fortec Motorsports, +1.299s
19. Josh McLean, Pace Performance, +1.517s
20. Jason Pribyl, ADM, +1.554s
21. Luca Magnussen, Fortec Motorsports, +1.569s
22. Megan Bruce, KMR Sport, +1.821s
23. Holly Miall, Fox Motorsport, +1.874s
24. Caitlyn McDaniel, Fox Motorsport, +4.837s
