As Musk schedules the rest of his day, he has to relentlessly prioritize. And that's his productivity recommendation for others, too.
"Focus on signal over noise. Don't waste time on stuff that doesn't actually make things better," he says.
For Musk the "signal" is product development, to which he dedicates the majority of his attention, according to an interview with Y Combinator president, Sam Altman.
"I think a lot of people think I must spend a lot of time with media or on businessy things," says Musk. "But actually almost all my time, like 80 percent of it, is spent on engineering and design. Engineering and design, so it's developing next-generation product. That's 80 percent of it."
In his free time, Musk says he likes to watch movies, hang out with friends and play first-person shooters with his kids. ("First-person shooters" are a type of video game where the player sees through the perspective of the main character and fires weapons.)