Tsuboi's quickest time of the day came late on in the two-hour morning session, as he posted a 1m18.150s to beat the ARTA Honda NSX-GT of Tomoki Nojiri by a scant 0.034 seconds.
Honda's three Bridgestone-shod cars, now using the Type S bodywork revealed last month, locked out positions two through four, with Real Racing newcomer Nobuharu Matsushita setting the pace in the afternoon session with a 1m18.215s set during the 10 minutes of GT500-only running.
The Kunimitsu Honda was third-fastest in the morning in Naoki Yamamoto's hands and fourth overall, just three thousandths behind the Real Racing car.
Completing the top six were two more Toyotas: Tsuboi's title-winning partner from 2021, Yuhi Sekiguchi, was fifth-fastest for new team SARD, while Kazuya Oshima was next up aboard the Rookie Racing car.
Fastest of the all-new Nissan Zs was the #3 NDDP Racing car, now run in-house by NISMO, as Mitsunori Takaboshi set the second-fastest time in the afternoon of 1m18.407s to go seventh overall.
The next-best Nissan was the Impul car in ninth with Kazuki Hiramine at the wheel, just behind the second TOM'S Toyota driven by Ritomo Miyata.
NISMO's flagship #23 car was 11th-fastest overall in the hands of Tsugio Matsuda.
GT300: JLOC Lamborghinis in control
In GT300, the #88 JLOC Lamborghini Huracan GT3 Evo ended up with the fastest time of the day, a 1m25.210s set by ex-Honda GT500 driver Takashi Kogure.
Shinichi Takagi, who has been reunited with old teammate Morio Nitta at the K-Tunes Lexus squad this year, was second-fastest on a 1m25.555s, followed by Kei Cozzolino in the Pacific CarGuy Racing Ferrari on a 1m25.898s.
The #87 JLOC car set the pace in the afternoon thanks to a 1m26.149s set by Natsu Sakaguchi, but Kosuke Matsuura's time in the morning put the second Lamborghini fourth-overall ahead of the UpGarage Honda NSX GT3 of SUPER GT rookie Kakunoshin Ota.
It was the UpGarage car that caused the day's third and final stoppage when it ground to a halt on track in the afternoon session.
The first two red-flag periods were triggered by offs for the #22 R'Qs Mercedes-AMG GT3, one in the opening minutes of the morning session and the other in the afternoon.
Okayama testing times (GT500 class):
Pos. | No. | Car/Team | Drivers | Morning | Afternoon |
---|---|---|---|---|---|
1 | 36 | TOM'S Toyota | Giuliano Alesi Sho Tsuboi | 1'18.150 | 1'19.195 |
2 | 8 | ARTA Honda | Tomoki Nojiri Nirei Fukuzumi | 1'18.184 | 1'18.501 |
3 | 17 | Real Honda | Koudai Tsukakoshi Nobuharu Matsushita | 1'18.227 | 1'18.215 |
4 | 100 | Kunimitsu Honda | Naoki Yamamoto Tadasuke Makino | 1'18.218 | 1'18.815 |
5 | 39 | SARD Toyota | Yuhi Sekiguchi Yuichi Nakayama | 1'18.314 | 1'18.965 |
6 | 14 | Rookie Toyota | Kenta Yamashita Kazuya Oshima | 1'18.396 | 1'18.566 |
7 | 3 | NDDP Nissan | Katsumasa Chiyo Mitsunori Takaboshi | 1'18.830 | 1'18.407 |
8 | 37 | TOM'S Toyota | Sacha Fenestraz Ritomo Miyata | 1'18.422 | 1'19.105 |
9 | 12 | Impul Nissan | Bertrand Baguette Kazuki Hiramine | 1'18.522 | 1'18.512 |
10 | 16 | Mugen Honda | Ukyo Sasahara Toshiki Oyu | 1'18.927 | 1'18.513 |
11 | 23 | NISMO Nissan |
Ronnie Quintarelli Tsugio Matsuda | 1'18.701 | 1'18.754 |
12 | 64 | Nakajima Honda | Takuya Izawa Hiroki Otsu | 1'18.702 | 1'19.466 |
13 | 24 | Kondo Nissan | Kohei Hirate Daiki Sasaki | 1'19.510 | 1'19.151 |
14 | 38 | Cerumo Toyota | Yuji Tachikawa Hiroaki Ishiura | 1'19.283 | 1'19.216 |
15 | 19 | Bandoh Toyota | Yuji Kunimoto Sena Sakaguchi | 1'19.328 | 1'19.320 |