Juan Mata scored the first league goal of the new era in the 40th minute and Wayne Rooney headed the second just before the hour.
Zlatan Ibrahimovic then marked his league debut by scoring with a low drive from 25 metres.
Mourinho said he was impressed by all facets of his team's performance.
"Everything, three points, the quality of our attacking football, the quality of our control, the quality of us defensively, obviously it's the premier league, one mistake you are punished immediately so one mistake, one goal."
