Oyu, fresh from scoring his first ever Super Formula pole last time out at Motegi, set his best time of 1m37.487s with around 15 minutes left on the clock in the 90-minute session on Friday afternoon.
That put him a comfortable 0.342 seconds clear of his nearest rival, Inging driver Sho Tsuboi, who led a flurry of improvements at the end of what proved to be an incident-free session.
Nojiri on the other hand experienced a difficult afternoon as he ended up 1.009s off the pace of Oyu.
The Team Mugen driver has the chance to become Super Formula's first back-to-back champion since Tsugio Matsuda in 2008, and could wrap up the title as early as Saturday's opening race.
A second-place finish, or third starting from pole, would be enough to put the title beyond the reach of his nearest rival in the championship, Sacha Fenestraz, whom he leads by 32 points.
Kondo Racing driver Fenestraz was third-fastest on a 1m37.966s, making him the final driver to clear the 1m38s barrier, while Ryo Hirakawa, the only other driver who remains in mathematical contention, was fifth-fastest for Impul on a 1m38.029s, just behind TOM'S driver Ritomo Miyata.
Yuhi Sekiguchi was sixth in the second Impul car ahead of Tadasuke Makino (Dandelion), who led the way on a 1m38.118s with 27 minutes remaining but slipped to seventh in the closing moments of the session.
Nirei Fukuzumi (Drago Corse), Kamui Kobayashi (KCMG) and Hiroki Otsu (Dandelion) completed the top 10, while Oyu's Nakajima Racing teammate Naoki Yamamoto ended the day 13th-fastest.
Nobuharu Matsushita, who won on Super Formula's previous visit to Suzuka in April, ended up 21st and last for B-Max Racing.
Qualifying for Saturday's penultimate round of the season will take place at 9.15am local time (GMT +9) ahead of the start of the race at 2.30pm.
Suzuka Super Formula (Rounds 9 & 10) - Practice results:
| Cla | # | Driver | Team | Time | Gap |
|---|---|---|---|---|---|
| 1 | 65 |  Toshiki Oyu |
TCS Nakajima Racing | 1'37.487 | |
| 2 | 38 | Sho Tsuboi |
P.MU/CERUMO･INGING | 1'37.829 | 0.342 |
| 3 | 4 |  Sacha Fenestraz |
Kondo Racing | 1'37.966 | 0.479 |
| 4 | 37 | Ritomo Miyata |
Kuo VANTELIN TEAM TOM’S | 1'38.015 | 0.528 |
| 5 | 20 | Ryo Hirakawa |
Team Impul | 1'38.029 | 0.542 |
| 6 | 19 | Yuhi Sekiguchi |
Team Impul | 1'38.045 | 0.558 |
| 7 | 5 | Tadasuke Makino |
Dandelion Racing |
1'38.118 | 0.631 |
| 8 | 12 | Nirei Fukuzumi |
ThreeBond Drago CORSE | 1'38.197 | 0.710 |
| 9 | 7 | Kamui Kobayashi |
KCMG | 1'38.217 | 0.730 |
| 10 | 6 | Hiroki Otsu |
Dandelion Racing |
1'38.300 | 0.813 |
| 11 | 15 | Ukyo Sasahara |
Team Mugen | 1'38.303 | 0.816 |
| 12 | 18 | Yuji Kunimoto |
KCMG | 1'38.303 | 0.816 |
| 13 | 64 | Naoki Yamamoto |
TCS Nakajima Racing | 1'38.392 | 0.905 |
| 14 | 3 | Kenta Yamashita |
Kondo Racing | 1'38.460 | 0.973 |
| 15 | 39 | Sena Sakaguchi |
P.MU/CERUMO･INGING | 1'38.485 | 0.998 |
| 16 | 1 | Tomoki Nojiri |
Team Mugen | 1'38.496 | 1.009 |
| 17 | 53 | Ren Sato |
Team Goh | 1'38.520 | 1.033 |
| 18 | 55 | Atsushi Miyake |
Team Goh | 1'38.644 | 1.157 |
| 19 | 36 | Giuliano Alesi |
Kuo VANTELIN TEAM TOM’S | 1'38.674 | 1.187 |
| 20 | 14 | Kazuya Oshima |
docomo business ROOKIE | 1'38.697 | 1.210 |
| 21 | 50 | Nobuharu Matsushita |
B-Max Racing Team | 1'38.816 | 1.329 |
| View full results | |||||
