Sebastian Vettel is not ruling out a return to Formula 1.

The four-time world champion appeared at the famous Goodwood Festival of Speed at the weekend with his personal collection of iconic historic F1 cars—all powered by sustainable fuels. His goal is to show that "you can have fun but perhaps in a more responsible way. It's something that maybe not everyone has fully understood yet," the 36-year-old German said.

Vettel thinks it's urgent for motor racing to catch up with the climate change debate because there is a risk that governments will ultimately ban such environmentally-harmful activities.

To that end, F1 CEO Stefano Domenicali has admitted that a role for Vettel as some sort of sustainability officer may be on the cards.

"We'll see, but I have some ideas," said Vettel. "I was in Monaco earlier this year. I had a very good meeting with Stefano."

Vettel says he has actually received "a lot of interest" to get involved in motorsport again, "but I made a goal last year that I want to be free. I say no to a lot of things because I want to get to know this version of myself that in a way doesn't know what to do.

"I also spend a lot of time with my children, but I don't want to live the lives of my children. That will not be my main task even if I want to be there for them. Sooner or later I will probably find a new challenge."