Speaking in an excerpt from the Apple Fitness+ podcast "Time to Walk," William, 39, recalled Diana playing "all sorts of songs" to help him and Harry quell anxieties about heading back to their boarding school.
"One of the songs I massively remember and has stuck with me all this time – I to this day still quite enjoy it, secretly – is Tina Turner's (The Best), because sitting in the backseat singing away, it felt like a real family moment," he said, recalling Diana "driving along, singing (at the) top of her voice."
Sometimes the police officer assigned to their family would join in on the singing, too, added the Duke of Cambridge.
"You'd be singing, listening to the music right the way up to the gates of school where they dropped you off, and that's when reality kind of sunk in: You really were going back to school, because before that you're lost in song," he said. "You want to play it again just to keep that family moment going. And when I listen to it now, it takes me back to those car rides and brings me back lots of memories of my mother."
Earlier this year, Harry admitted to a fractured relationship with his brother during his and Duchess Meghan's bombshell interview with Winfrey.
The two brothers came together in July for the unveiling of Princess Diana's new statue on what would have been their late mother's 60th birthday. They smiled for photographs and released a joint statement ahead of the unveiling honoring their mom.
"We remember her love, strength and character – qualities that made her a force for good around the world, changing countless lives for the better," they said.
The full 38-minute episode is available to stream for Apple Fitness+ subscribers, and can be heard by the general public during three live airings on Apple Music 1, the brand's global radio station, on Monday at 11 a.m. and 4 p.m. ET.
William will talk about the "importance of keeping mentally fit" as well as "a lighthearted moment when he was drawn out of his comfort zone, the value of listening as a way to empower others and an experience that led him to prioritize mental health," according to an Apple news release.
The "Time to Walk" podcast features different famous guest hosts each episode who are invited to share "lessons learned, meaningful memories, thoughts on purpose and gratitude, moments of levity, and thought-provoking topics" while walking through a location meaningful to them.
Past guests this season have included Dolly Parton, Jane Fonda, Naomi Campbell, Draymond Green, Dr. Sanjay Gupta and Kesha.
Contributing: Amy Haneline
This article originally appeared on USA TODAY: Prince William on singing with Princess Diana: 'Time to Walk' podcast