United ruthlessly despatched Roy Hodgson's struggling Palace to condemn the Eagles to a seventh straight league loss without scoring.
The Reds have now scored four goals in a game six times and the result matched United's best-ever tally of 19 points after the opening seven Premier League matches - set in 1999 and 2011.
By contrast, Palace have made the worst start ever by a team in the top four divisions of professional football.
Hodgson, who replaced the sacked Frank de Boer last month, faces arguably the toughest challenge of his veteran managerial career to turn around their seemingly irreversible fortunes.
The result saw the Reds - albeit temporarily - move three points clear at the top of the Premier League, although City leapfrogged back over us with their own impressive 1-0 win at champions Chelsea.
Juan Mata's first goal of the season set United on their way, before Marouane Fellaini scored twice and Romelu Lukaku added the fourth late on.
The Belgian now has eleven goals in ten games and matched Andy Cole's record of seven in his first seven United league matches.
Phil Jones, Fellaini and Valencia all came back in, but any fears of a sluggish start following those midweek exertions were quickly banished.
United moved ahead inside five minutes when the recalled Mata steered home from ten yards after excellent wing work from Marcus Rashford,
David de Gea saved well from Bakary Sako and Yohan Cabaye fired wide from distance but, against the run of play, the Reds moved 2-0 ahead ten minutes before the break.
Ashley Young crossed for Fellaini who volleyed home from all of a yard at the back post.
Four minutes after the interval the Reds put the result beyond doubt - if it wasn't already - when Rashford's free-kick picked out Fellaini who headed in for his first brace for United.
Young tried his luck with a 20 yarder, while at the other end Sako miscued a header and then blazed over the bar as Palace searched for their elusive goal.
Lukaku dragged his shot uncharacteristically wide, but the big striker was not to be denied and he completed the rout moments later.
He matched Cole's mark when substitute Anthony Martial made his mark again as he pulled the ball back and Lukaku tapped in from close range.
United go into the two-week international break level on points with City and just one goal worse off, with the trip to Anfield looming large as our toughest test of the season so far.
Overall team performance: 8/10
United Faithful Man of the Match: Marouane Fellaini