Marcos Ambrose has opened up on his decision to retire from V8 Supercars in 2015, just months after returning to the sport.

The Tasmanian won championships in 2003 and 2004 before moving to the USA to chase a career in NASCAR.

Starting in the truck series in 2006, Ambrose moved up to the top-level Sprint Cup series in 2009 and completed six seasons.

Ambrose then made the jump back to V8 Supercars when the American group Team Penske joined forces with Dick Johnson Racing.

He competed in the final round of the 2014 season and the first of 2015 before coming to the realisation it was no longer for him.

"The burnout was certainly there," he told respected commentator Greg Rust during a Q&A at the CAMS awards night on Saturday.

"That's why when I came back to Australia I realised that I wasn't the right person to lead Dick Johnson/Team Penske on. I've paid my price in racing. Forty races a year plus all the other show events you do throughout the season, you supersize a whole career in one season over there. That's just a fact of life. A lot of drivers do burn out."

View photos Marcos Ambrose at the 2015 Clipsal 500. Pic: Getty More

Ambrose did compete in the endurance races in 2015 at Sandown, Bathurst and Surfers Paradise, while his 2016 was clear after he realised his "time was up".

Now 40, he said discussions with Penske kicked off 18 months before the team confirmed its Supercars intentions.

Acknowledging that his situation was an elephant in the room, he said the lag time proved problematic.

"A year and a half later the phone call comes and it's on. And it’s like, ‘oh s***, is this really what I should be doing now? Because I’m feeling pretty tired and worn out from my American thing'. I thought it’d be right, I’ll come home and it’ll work itself out," he said.

"And then the situation that DJR was in at the time, where they were in this transition phase – and they still are, they’re still getting better and better each race, you can see their progression – but it just takes time. I knew it.

View photos Ambrose at his final NASCAR race. Pic: Getty More

"So when you come back, and I’m struggling to adapt from NASCAR back into a modern V8, the testing restrictions, and the tyres are hard, and I’m kind of confused and tired from the States. And then you see, of course, ‘s***, to get out of this is going to take three years, to dig yourself out of this hole'.

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