Tom Cleverley's first league goal at Old Trafford and Wayne Rooney's fifth in four games were enough to keep United six points clear of neighbours City, with Frazier Campbell's header against his old club scant consolation for the Wearsiders, who remain deep in relegation trouble.
Yet perhaps the most significant moment of the entire game came with Nemanja Vidic's introduction midway through the second-half.
Plagued by injuries since August 2011, Vidic's absence during last season's run-in contributed to United's defensive wobbles and the Serbian is viewed as the main way of plugging the leaks that have been so obvious for a side who have still only kept three clean sheets all season.
Patrice Evra had already wasted one excellent opportunity when Ashley Young wriggled away from Carlos Cuellar close to the dead-ball line, then cut a cross back which Van Persie finished expertly.
Within three minutes, the hosts had their second. It was a gem too as Cleverley exchanged passes with Michael Carrick before drilling an excellent effort past Simon Mignolet from 12 yards.
Half-time was approaching before Sunderland carved out their first meaningful opportunity, which Stephane Sessegnon struck Evra with before it flew over.
There was little argument to be made for a Black Cats comeback and any pretence was ended just before the hour when an unselfish overlapping run by Van Persie was followed by a deft piece of skill that took him between Cuellar and Titus Bramble before he set up Rooney, who tapped home from close range.
With victory assured, Sir Alex Ferguson felt sufficiently confident about easing Vidic back into the fray. After only 13 appearances in a 16-month period that included a calf injury and two lots of knee surgery, the 31-year-old desperately needs to stay injury free in order to rediscover his old form.
Evidently, Vidic has plenty of work in front of him too judging by the uncharacteristic mistake that eventually led to United old-boy Campbell heading home from close range.
Source: PA
Source: PA