Sasahara and Oyu finished third in last Sunday's sixth round of the season, taking advantage of the Dunlop tyre's speed in what was the first wet SUPER GT race for three years.
With the two Michelin-shod Nissan Zs finishing first and second, it was the first race of the season not to feature at least one Bridgestone car on the podium.
Sasahara took over from starting driver Oyu on lap 36 of 84 and withstood pressure from the best-placed of the Bridgestone cars, the Cerumo Toyota GR Supra, in he latter part of the race to secure third.
But despite scoring a first podium finish since 2020, he feels the result was more a reflection of how Bridgestone struggled in the rain than any major progress with the Mugen-Dunlop package.
"Surprisingly, the Bridgestone teams were not fast when they switched to wet tyres, and that was a factor," Sasahara told Motorsport.com's Japanese edition.
"It looks like a good situation at first glance, but I can’t say with big confidence that we are in great shape or anything."
However, Sasahara also acknowledged that the speed of the Dunlop slick on a slightly damp track was also vital to finishing on the podium.
"The conditions were still difficult, but when I using slicks the Dunlop tyre showed a great performance on a slightly wet track, and that allowed me to stay calm and control the gap to the car behind," he said. "I'm grateful for that."
Oyu was at the wheel of the Red Bull-sponsored Honda during the initial rain shower, and enjoyed a spell in the lead of the race as most of the other GT500 runners pitted for wet tyres before Mugen called him in on lap 19.
The 24-year-old opined that Dunlop correctly predicting the unstable weather was another factor in he and Sasahara being able to score their first podium finish as a duo in their second year together.
"I think it’s true that the tyres are getting better," said Oyu. "We imagined the conditions might end up being something like this and we prepared accordingly, and it worked well.
"Basically we need to improve the base of the car, but it is getting better little by little. Against that backdrop the way the race unfolded played into our hands, and by doing a good job and enduring the conditions it turned out to be a good race."
Sasahara and Oyu now head to the penultimate round of the season at Autopolis, where they started from pole position last year only to lose the chance of a victory due to a detached wheel.
"We were almost able to win at Suzuka [Round 5] as well, but it turned out to be one of those races," said Oyu, referring to the timing of the safety car that ruined Mugen's pit strategy. "But the team has grown because of those experiences and I want to make use of the team’s strength.
"Our success weight will increase, but I want show the kind of performance that would allow us to start from pole again [at Autopolis]."
- Stream every qualifying session and race of the 2022 SUPER GT season only on Motorsport.tv.
