A passion project for Bay, who has made Paramount a fortune with his "Transformers" franchise, "Pain & Gain" was shot for a modest $26 million, spare change compared to the director's usual budgets.
The movie has the director taking a breather from his usual sci-fi action spectacles for a story based on a kidnapping-extortion caper carried out by bodybuilders in the 1990s. Yet "Pain & Gain" still has Bay's usual visual flair, and the reviews generally were better than what he's used to.
"With that kind of budget, to open to $20 million the first weekend is a very strong opening," said Don Harris, Paramount's head of distribution. "You see what a director really in his prime, at the top of his game, can do with a small budget, what he can make a movie look like."
"Oblivion" was down a fairly steep 53 percent from the movie's $37.1 million domestic debut the previous weekend.
Overseas, "Oblivion" took in $12.8 million to lift its international haul to $134.1 million and worldwide total to just under $200 million.
Hollywood's domestic downturn continued, with revenues totaling $90 million, off 18.5 percent from the same weekend last year, when "Think Like a Man" led with $17.6 million, according to box-office tracker Hollywood.com.
Receipts have trailed 2012's for most of the year, with 2013 domestic ticket sales running at $2.9 billion, nearly 12 percent behind last year's.
That pattern could continue as Hollywood opens its summer season domestically this coming weekend. Despite a huge haul expected for "Iron Man 3," the film will be competing against that gigantic start over the same weekend last year for "The Avengers," the only movie to open with more than $200 million domestically.