United was leading 2-0 at half time as Marcus Rashford and Anthony Martial had scored a goal each.
Nicolás Otamendi tried to give the hosts some hope in the 85th minute of the match but that was not enough.
Manchester is third on the points table with 32 points, United in fifth with 24 points while Liverpool remains at the top with 46 points.
In other matches played this morning, Everton beat Chlesea 3-1 Liverpool beat Bournemouth 3-0, Tottenham beat Burnley 5-0 while Watford and Crystal Palace finished the match scoreless.
