Bowers' agent, David Kuhn, said he died Sunday of natural causes at his home in Los Angeles.
A native of Ottawa, Illinois, Bowers was a Marine who served in the Pacific during World War II and moved to Los Angeles after the war ended. He found work in 1946 at a gas station on Hollywood Boulevard, and later contended his life changed when the actor Walter Pidgeon drove up in a "shiny" Lincoln two-door coupe and asked, "What are you doing for the rest of the day?"
"The gas station was the portal that eventually took me into an exclusive world where high-class sex was everything," Bowers wrote in "Full Service: My Adventures in Hollywood and the Secret Sex Lives of the Stars," published by Grove in 2012.
Bowers switched jobs from gas attendant to bartender and was welcomed, however discreetly, into the Hollywood underground and party scene. He kept planned assignations in his head, not on paper, and managed to avoid both vice squads and the tabloids in a more censorious, pre-TMZ world. In "Full Service," he told some of the industry's most shocking stories since Kenneth Anger's notorious "Hollywood Babylon."
At a time when Hollywood nicknames included "Duke" (for John Wayne) and "Bogie" (for Humphrey Bogart), Bowers was known as "Mr. Sex." He wrote of orgies with Cole Porter, "sexual mischief" with Grant and actor Randolph Scott, giving Vivien Leigh "orgasm after orgasm" and affairs with J. Edgar Hoover and Spencer Tracy. He also alleged that he found partners for everyone from Hepburn and Grant to the Duke and Duchess of Windsor.
"His idea of good clean fun included drilling a peephole in the gas station's bathroom," The New York Times' Janet Maslin wrote in 2012, "exercising his healthy libido so fully that he sometimes needed an ice pack to recuperate, and providing fake college girls to serve as the real college girls cited in Alfred Kinsey's scientific sex studies."
Bowers was the subject of a 2018 documentary, "Scotty and the Secret History of Hollywood," directed by Matt Tyrnauer.
Critics were skeptical, and Tracy biographer James Curtis dismissed Bowers as "full of glib stories and revelations, all cheerfully unverifiable." But he also had numerous defenders, including the writer Gore Vidal, to whom Tyrnauer dedicated his film.
"Scotty doesn't lie," Vidal wrote in a blurb for the book, "the stars sometimes do — and he knows everybody."
Bowers would allege that he had adult encounters since age 11, when a Catholic priest in Chicago would pay $1 for favors. He finally settled down in the 1980s, writing that the AIDS epidemic meant that "it was too unsafe a game to play anymore," and married speech therapist Lois Broad in 1984. Bowers waited decades to tell his story in part because some of his alleged former clients and lovers were still alive.
"I've kept silent all these years because I didn't want to hurt any of these people," Bowers told the Times in 2012. "And I never saw the fascination. So they liked sex how they liked it. Who cares?"