According to Walkinshaw Andretti United, the change was made as part of the impending switch to Toyota – with WR29 set to be converted to a Supra and act as the spare car next season.
The switch did, however, coincide with a patchy run of form for Mostert, particularly in comparison with high-flying teammate Ryan Wood.
Mostert made good use of his return to WR28 in Townsville, out-pacing Wood across the weekend and scoring podiums in two of the three races.
Beyond the results, Mostert felt the change meant he and Wood were speaking the same language regarding car behaviour, something that had been lost in recent events.
“I’ve definitely felt like we’ve had a little bit of deficiency in the last car, which we were still struggling to get our head around,” said Mostert when quizzed by Speedcafe.
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“We’ve made a lot of changes in the off-season, which this weekend, going back to the old car, was pretty much how we would run a car last year.
“The two cars this weekend really lined up a lot with the data and both drivers had the same comments of what we were trying to chase and trying to find.
“We’ve probably been a little bit different in the last couple of rounds, trying to chase a few different weaknesses.
“So it was just nice to be able to, with what Woody’s feeling in his car, and what I felt in the car this weekend, it was pretty similar.
“It just makes it back to fighting as a two-car team and trying to work on the same problems.”
WAU is planning on two ground-up builds for the Supras that will make their race debut at the opening round next season.
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