The entire Supercars field ran its Gen3 cars together for the first time today in a single, crucial all-in test at Sydney Motorsport Park.

The first opportunity to gauge comparative performance came amid an ongoing parity saga with the new cars, as Ford continues to voice concerns over aero and engine performance compared to the Camaro.

Supercars is set to head back to the runway for more homologation testing next week, while tweaks to engine mapping for both the Ford and Chevrolet teams continued today, with sources indicating the Chevrolet shift cut was slowed.

By the end of the day there was a clear trend of dominance from the Chevrolet teams as Brad Jones Racing's Andre Heimgartner edged Erebus driver Will Brown in the afternoon session to secure the top spot. Only one Mustang driver, Todd Hazelwood (Blanchard Racing Team), snuck into the top 10 in ninth.

Brodie Kostecki was third fastest while Macauley Jones, Jack Smith and Bryce Fullwood all banked late laps to make it an all-BJR/Erebus top six.

A number of those laps came during an additional 15 minutes of running added to the cut-off after Nick Percat stopped with a loose wheel on his WAU Ford inside the last 10 of the scheduled minutes.

Chevrolet's dominance of the timesheets has raised eyebrows from leading GM-aligned teams, Erebus Motorsport boss Barry Ryan adamant the Ford teams were purposely not trying for a fast time.

"I know they weren't," he told Autosport. "They may have been trying hard, but they weren't tyres that give you lap time.

"I was out there all day watching it because we were all wary of it. And when they're just on hard tyres, and you can tell an old soft tyre because the white is gone off the side, it's ridiculous.

"There will be reports tonight that there's only one Ford in the top 10 – and I don't give a shit. I trust the VCAT system and that's proven itself over the years. We haven't had a parity issue since Ford did the same thing last time."

Triple Eight team manager Mark Dutton added that some gamesmanship from Ford would be normal given the circumstances.

"You'd have to think there's a bit of that going on," he said. "There are some very smart people in those teams that like that gamesmanship.

"But I didn't see what [tyres] they were on when they were on their fastest laps. Because of the weather we weren't mandated to run [new] tyres at the end."

Several Ford teams denied any allegations of sandbagging, including Grove Racing's team principal David Cauchi.

"We were out there on soft tyres at the end of the day," he said. "We were running through our programme. We weren't trying to do a time as such, but we were trying to go fast.

"There was no concerted effort to not go fast, at least not from our team."

Despite his claims of gamesmanship, Ryan remains confident that the VCAT re-run next week will yield the right outcome.

"It will make everyone at ease," he said. "The biggest thing I saw on the data screen was that the cars were all within a kilometre of an hour of each other. And it was a mixture of cars. It's pretty bloody impressive. Supercars should be proud they've got to that point.

"If the aero is a bit different, and [Ford] chooses to have that balance, well that's fine.

"We'll see. When the chequered flag drops in qualifying in Newcastle, we'll know."