Australians Adam Scott and Cam Davis set themselves up for top-10 finishes but the chasing pack will be playing catch-up on championship Sunday after Scheffler surged three shots clear with a majestic six-under-par 65.
Scheffler started his big run with a three wood to just inside three feet on the reachable par-4 14th for an eagle, causing so much hysteria that Bryson DeChambeau had to back off his putt across the lake at the 17th.
The masterclass ended with an eight iron from the seam of a divot to just inside 10 feet for birdie on the 18th, creating even more space between Scheffler and Swede Alex Noren, who had a 66 and gets his first shot in a final group alongside the No.1 player in the world.
DeChambeau, the US Open champion who has been a major force at golf's biggest events, briefly took the lead with a birdie on the par-5 15th. And then it all came undone.
He missed a four-foot par putt on the 16th, found the water on the par-3 17th after the cheer for Scheffler made him back off a 25-foot bogey putt that he eventually missed.
DeChambeau had to scramble for par to salvage a 69 that felt much better but he will still enter the final round six behind.
Scheffler is at 11 under and very much the man to beat as he closes in on a third career major title.
"Big emotion for me," said Scheffler on the first anniversary of his dramatic arrest during last year's PGA Championship at Valhalla.
"I wanted to finish off the round the right way. I hit some good shots down the stretch."
When it was all said and done, after seven birdies and an eagle from Scheffler, Noren was his closest pursuer after closing with four birdies in his last five holes.
Americans Davis Riley (67) and North Carolina native JT Poston (68) were at seven under and four behind.
The third round was delayed by morning storms, forcing a change in tee times to threesomes off both tees that didn't start until shortly before noon.
And then it became a game of musical chairs for the lead. Nine players had at least a share of the lead at one point.
One of them was two-time major champion Jon Rahm, who has not seriously contended in the four majors he has played since joining LIV Golf.
"Hard to express how hungry I may be for a major, about as hungry as anybody can be in this situation," Rahm said. "Very happy to be in this position."
Rahm is tied for fifth with Si Woo Kim (71) and Jhonattan Vegas, who had two-shot leads after 18 holes and 36 holes and began Saturday with two straight bogeys.
Vegas steadied himself and was still in the mix until driving into the water on the 15th for bogey and finishing out his 73 with a three-putt going on the 18th.
Contesting his 25th PGA Championship, Scott will enter the final round seven shots behind Scheffler in a tie for 13th after carding a steady two-under 69.
Tied for fourth at Oakmont two years ago, Davis is another stroke back in equal 17th after igniting his round of 70 with a hole-out eagle three after two successive birdies on his homeward nine.
Elvis Smylie, the only other Australian to make the halfway cut, stumbled with a 77 to slip to seven over and joint 69th.
With The Associated Press
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