Andretti's major Walkinshaw Supercars coup

Laine Clark
There are blue skies ahead for Walkinshaw Racing after the team partnered with Michael Andretti

In the end, the motivation behind US motorsport great Michael Andretti's landmark decision to buy into battling Supercars outfit Walkinshaw Racing was simple.

"Any chance you get to beat Roger Penske, you take it," Andretti said.

Andretti will renew his age-old IndyCar rivalry with legendary team owner Penske in Australia next year, with Walkinshaw Racing (WR) dropping their bombshell on Thursday night.

Five months before the touring cars are unleashed for another year, WR is set to become a powerhouse again. IndyCar heavyweight Andretti Autosport and McLaren Formula One chief Zak Brown's United Autosports confirmed they would buy into the once-mighty Holden team from 2018.

From January 1, the team will be known as Walkinshaw Andretti Autosport, pending Supercars' approval.

WR team boss Ryan Walkinshaw and Andretti will be equal stakeholders, with Brown holding a minority share.

It is a game changer.

Five-time Indy 500-winning team owner Andretti is part of American racing royalty.

And Brown was the man touted to take over from Formula One boss Bernie Ecclestone.

The forgotten ex-factory-backed WR outfit, which had once boasted Peter Brock, Craig Lowndes and Mark Skaife, has all the resources in the world to return to Supercars' summit.

Walkinshaw described it as a "beginning of a new era" in Supercars.

Andretti - trackside at Mount Panorama ahead of Sunday's Bathurst 1000 - saw it as another chance to take down his nemesis Penske.

"He's the benchmark in the sport," Andretti said of his long-time rival.

"If you can beat him, you can beat anybody.

"So I am very excited to go head to head with him again."

WR will hope to replicate Penske's success since his Supercars entry in late 2014.

He took a major share in Dick Johnson Racing to form DJR Team Penske - a partnership dominating the Supercars championship.

Scott McLaughlin and Fabian Coulthard are first and third respectively heading into this weekend's race.

Andretti - the son of motorsport great Mario - is also one of the most-successful drivers in American open-wheel history.

Since retiring from driving, Andretti began his own IndyCar team featuring his son Marco and a team in the FIA Formula E Championship and the Global Rallycross Championship.

Penske Corporation's executive vice-president Bud Denker welcomed Andretti's challenge.

"Michael's legacy is terrific on its own but, with Zak also involved, I think it shows the confidence people overseas have in this series," he said.

"They wouldn't be getting involved if they didn't think this is a great place to grow your brand.

"Any news is good about a team coming in, particularly those two."

It is a coup for WR, whose future had appeared in doubt after losing their 2017 Holden factory backing after 26 years in a shock move announced in 2016.

Their fortunes haven't changed this year - drivers Scott Pye and James Courtney are 18th and 19th respectively in the standings.

WR are a distant sixth in the Supercars teams' championship.

Walkinshaw said bringing in a new manufacturer to the category was their key objective but dismissed speculation they would use Chevrolet Cameros in the future.

"Our ideal situation will be to continue running Holdens next year but there will be a renewed focus from myself and Michael to go and search for a new manufacturer going forward," Walkinshaw said.