The world No.1 birdied the first five holes at TPC Southwind and added a sixth at No.7, in the first leg of the playoffs on Friday in Memphis.
Bogeys at Nos.8 and 12 around one birdie at No.10 took him off the pace for a possible sub-60 round, but he carded four more birdies over the final six holes to break from the pack.
At 11-under 129 at the halfway mark, Scheffler caught Friday's early leader, South Korea's Sungjae Im, and gained a three-shot advantage as he seeks his first win since January.
"You always want to try to get off to a good start," the American said. "I was able to do that today.
"Really just a dream start. Probably one of the best starts I've had on tour, to be honest with you."
Scheffler was No.1 in the FedEx Cup points race entering the week, so a victory changes nothing about his position.
Im, however, is No.53 in points and trying to climb into the top 50 to qualify for next week's BMW Championship.
His second consecutive 66 puts him in striking distance entering the weekend. Im birdied the first three holes Friday and went out in 5-under 30 before two bogeys sandwiching one birdie late in his round.
Sweden's Ludvig Aberg shot a 65 to get to seven under, and Viktor Hovland (64) of Norway was tied with him for third.
The back nine proved to be the nemesis for Adam Scott (70) and Min Woo Lee (71).
Scott is tied 14th at four under and could have been much higher in the field had it not been for bogeys on the 15th and 17th.
Lee fell 14 spots into a tie for 27th after finding trouble on the par-four 12th where he made double-bogey, before dropping a further shot on the 16th.
But both Australians are well inside the top 50 - Lee currently 18th and Scott 26th.
Germany's Matty Schmid, who is tied 54th and currently sits at No.70 in the rankings, needs all the help he can get to keep his season alive.
Schmid (70), at three over, aced the fourth to do his chances a world of good.
Japan's Ryo Hisatsune followed his 69 with a 70 to be at one-under, his round including an eagle on the 16th thanks to a great deal of fortune.
None of the five first-round leaders co-leaders matched their opening rounds of 65. Jordan Spieth carded a one-under 69 to get to six under, where he was tied with reigning FedEx Cup champ Tommy Fleetwood (66) and Colombia's Nico Echavarria (66).
Rory McIlroy of Northern Ireland fared better after a rough four-over 74 to begin the tournament, but back-to-back bogeys at Nos.17 and 18 left him with an even-par 70 and four over for the week.
with AAP
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