Reece Ushijima left the rest well adrift after his 2:05.172s put him a cut above anyone else on the Formula 3 grid.
The Van Amersfoort Racing man ended the session over a second clear of anybody else, with Campos Racing enjoying a 2-3-4 as his closest challengers.
Cars filtered out onto track under grey skies and a little bit of drizzle. The flashing lights on the rear wings were blinking as drivers got to grips with the cool conditions around Spa-Francorchamps.
Jenzer Motorsport’s William Alatalo set the first representative time on a 2:09.590s but that was bettered by Carlin driver Brad Benavides with the American setting a 2:09.421s soon after.
The times continued to tumble as the clock ticked under half an hour remaining of the Practice session. Title contender Victor Martins struck first, lowering the benchmark to a 2:07.381s to go half a second clear of anybody in P1.
Laps from the MP Motorsport and PREMA Racing trios closed that gap down to a quarter of a second and Ushijima slotted himself into second, one-thousandth of a second up on Kush Maini in P3.
Trident then popped up to go 1-2-3 all within a tenth of one another but that lock-out didn’t last long either. It was then Oliver Bearman’s turn to go fastest, setting a 2:06.798s to seal the top spot approaching the halfway point in the session.
Roman Stanek came to a halt on the Kemmel Straight with just over 10 minutes remaining of the session, briefly bringing out yellow flags before the Trident driver was able to get his car restarted to continue.
Into the final five minutes and Hadjar was able to find improvements in the second and third sectors to take the top spot from Bearman with a 2:06.639s.
Campos Racing’s Oliver Goethe was the next to go fastest, 0.4s clear until Ushijima smashed the benchmark by over a second, lowering the target to a 2:05.172s
A late effort by Josep María Martí made it a Campos 2-3-4 at the chequered flag, but nobody could get within a second of Ushijima’s stunning lap.