Supercars great Mark Winterbottom has made the stunning admission that he is leaving Ford because his car can't compete with Holden's Red Bull Racing (RBR).

The ex-series champion dubbed "Frosty" will draw the curtain on his 13-season career at Ford heavyweights Tickford Racing at this weekend's season finale Newcastle 500 after signing with Holden's Irwin Racing for 2019.

The 2014 Bathurst 1000 winner will next year replace Lee Holdsworth at Irwin Racing in a Commodore constructed by Triple Eight Engineering, the same makers for all-conquering Holden outfit RBR.

Shane van Gisbergen will try to extend RBR's dominance when he fights it out with Ford's Scott McLaughlin for the 2018 series championship at Newcastle.

RBR have produced eight championship winners in the past 10 years.

Winterbottom may still have one round left in Ford colours but the 2015 series champ was already excited by the prospect of lining up against RBR in a Triple Eight-made Holden.

"I've tried so many years to beat them, (spilt) blood, sweat, tears, hours and hours trying to beat that team (RBR)," Winterbottom told Fox Sports.

"They're a great team. The results don't lie.

"There's a point where you try so hard to beat them and you can't.

"I'm looking forward to trying to drive that car and now go against them in the same equipment.

"I feel good about that."

Irwin Racing is a stand-alone team owned by Charlie Schwerkolt.

But Winterbottom said his new outfit would have close ties with Triple Eight, who make Commodores for every Holden Supercars team except Walkinshaw Racing.

"(RBR's Jamie) Whincup to his credit said to me 'you've made the right move, you're going to love our equipment' at New Zealand (last round)," Winterbottom said.

"Hopefully we're all up there fighting for a championship and we're part of that mix."

Winterbottom admitted it was "weird" leaving Ford.

"It's a bit of a shock. Your whole career's been a blue badge," he said.

"It feels weird. People in the street where we live are going to think they're new owners because they've never seen a Holden in our driveway.

"But I want to win. I'm joining this team because I believe I can win and that's part of it."

Australian Associated Press