The Ford Mustangs have been given a parity-related tweak for the Penrite Oil Sandown 500.

It is understood that the shift cut in the Mustang was shortened overnight, ahead of this morning’s fourth Repco Supercars Championship practice session of the weekend.

In a move which mimics what is thought to have occurred at least once earlier this year, the cut is believe to have been shortened from the standard 50ms to 30ms for the higher gear changes, from third upwards.

The Chevrolet Camaros remain on the 105ms cut which they have had for most of the year, although it is believed that the cut was backed off to 80ms during the Sydney Motorsport Park event.

On the empirical evidence, it appears that the change at Sandown has helped the Mustangs.

Although today’s Qualifying session was another Camaro one-two-three, six Mustangs made this afternoon’s Top 10 Shootout whereas Friday practice ended with no blue in the top eight.

However, it does create a question mark as to how the Mustangs will fare in tomorrow’s 161-lap race.

There have been concerns for most of the season about how the Fords wear out their tyres quicker than the Chevrolets do, and a quicker shift cut could well exacerbate that issue.

Tyre life is already in sharp focus for both sides of the brand divide this weekend, given the super soft tyre allocation and the abrasive nature of the ageing Sandown surface.

While no compulsory pit stops are mandated for tomorrow, and fuel range could exceed the 54-lap minimum for any individual driver, there are suggestions that some cars may still make four stops during the race.

The Top 10 Shootout starts at 17:20 local time/AEST.