Ryan Giggs scored on his 999th senior appearance for club and country to help lift Manchester United 15 points above Manchester City with victory over QPR.
The Welshman sealed the win after Rafael's spectacular 20-yard strike had given the visitors a first-half lead.
The young Brazilian also showed his worth in defence when he cleared Chris Samba's header off the line.
QPR improved after the break but Giggs timed his run to tuck in with 10 minutes left and later hit the bar.
Rafael strike unbelievable - Ferguson
A stinging shot from Loic Remy was saved by David De Gea and it had looked like United might have to endure a nervous finish before Giggs's intervention settled the contest.
In the end, there was time for Danny Welbeck and Wayne Rooney to waste further chances, as United inflicted a defeat that leaves QPR rooted to the bottom of the Premier League, seven points from safety.
Manchester City, who face third-placed Chelsea on Sunday, now face a huge task to catch United with 12 games remaining.
The only minor worry for the league leaders was an injury to Robin van Persie as the striker set up Rafael for the opener.
The Dutchman was replaced before half-time after suffering what looked like a hip injury as he fell down a cameraman's bunker behind the goal-line.
The visitors had already threatened through Javier Hernandez's early header before Rafael struck, and QPR were scarcely helping themselves by continually giving the ball away.
Happy hunting ground
Manchester United's victory extended an unbeaten run at Loftus Road stretching back to 1989. They are also unbeaten against QPR in the Premier League.
It was one such loss of possession that led to the opening goal. Adel Taraabt was dispossessed by Giggs, who fed Van Persie and when Julio Cesar palmed away the Netherlands international's cross, the ball fell to Rafael, who sent his shot into the top corner.
Andros Townsend fought back for QPR, demonstrating some neat skill but unable to find a finishing touch. The hosts then came close to an equaliser when Rafael cleared centre-half Samba's header off the line.
Rafael was turning in a performance to back up Sir Alex Ferguson's recent assessment of the 22-year-old as a maturing presence, and moments later the right-back raced to the other end and provided a floated cross for Van Persie, but the striker's measured volley was tipped away by Cesar.
That was the last meaningful action for Van Persie, who was replaced by Welbeck. But the change did little to disrupt United's dominance - Nemanja Vidic should have done better from Giggs's cross but headed over from six yards out.
Redknapp confident QPR will survive
Jose Bosingwa, making his first appearance since 8 December following a reported fall-out with QPR boss Harry Redknapp, had a busy afternoon at right-back as United probed down the left through the dangerous Ashley Young.
QPR retained possession better after the break and had chances to equalise when De Gea stopped Remy's strike, before keeping out another Samba header.
But just as the hosts were beginning to build some momentum, Giggs - whose 999 games include 64 for Wales and four for Great Britain in addition to his 931 for United - latched onto Nani's pass to score his 168th club goal and demonstrate yet again his enduring value to United.
Manchester United manager Sir Alex Ferguson:
"It was a great result for us. It's another game away so it's important, we are 15 points ahead at the moment.
"It was one of these games where the pitch was lively, the ground was tight. There wasn't a great deal of football in the first half to be honest, it was a display from us which was more about determination, concentration and defending and we got through it."
QPR boss Harry Redknapp:
"I thought we were bang in the game, then little right-back hits a 'worldie' - he won't hit another goal like that as long as he plays football.
"He's hit one out of the clouds that's gone in the top corner. Up until then there wasn't a lot in it.
"This leaves us bottom today, but we won't be bottom at the end of the season. I still feel we'll get out of it. You probably think I'm mad, but I don't think I am. Everybody else has written us off, but I haven't. I still feel we have a chance."
Full Time The final whistle goes and the game is over.
Adel Taarabt takes a shot from 20 yards. Blocked by Rio Ferdinand.
David Hoilett fouled by Rafael Da Silva, the ref awards a free kick. The ball is swung over by Adel Taarabt, Header from close in by Christopher Samba hits the post.
Adel Taarabt takes the chance to get an effort at goal. Michael Carrick gets a block in.
Free kick awarded for an unfair challenge on Armand Traore by Antonio Valencia. Clint Hill restarts play with the free kick.
Wayne Rooney produces a right-footed shot from just outside the box that misses to the right of the goal.
Shot by Ryan Giggs. Effort on goal by Luis Nani from deep inside the area goes harmlessly over the bar.
Inswinging corner taken left-footed by Ryan Giggs from the right by-line to the near post, Clint Hill makes a clearance.
Assist on the goal came from Luis Nani.
79:16 Goal scored
Goal! - Ryan Giggs - QPR 0 - 2 Man Utd Ryan Giggs finds the back of the net with a goal from inside the box to the bottom right corner of the goal. QPR 0-2 Man Utd.
Wayne Rooney takes a shot. Christopher Samba gets a block in.
Substitution David Hoilett comes on in place of Andros Townsend.
Adel Taarabt is ruled offside. David De Gea takes the direct free kick.
Free kick awarded for an unfair challenge on Wayne Rooney by Christopher Samba. Rio Ferdinand restarts play with the free kick.
Jermaine Jenas fouled by Danny Welbeck, the ref awards a free kick. Direct free kick taken by Clint Hill.
Substitution Antonio Valencia is brought on as a substitute for Ashley Young.
Adel Taarabt takes the inswinging corner, Close range header by Christopher Samba misses to the right of the target.
Loic Remy produces a drilled right-footed shot from 12 yards. Save by David De Gea.
Unfair challenge on Danny Welbeck by Clint Hill results in a free kick. Free kick taken by Rio Ferdinand.
Substitution Wayne Rooney replaces Javier Hernandez.
Substitution Loic Remy joins the action as a substitute, replacing Bobby Zamora.
Foul by Clint Hill on Rafael Da Silva, free kick awarded. The free kick is delivered left-footed by Ryan Giggs from right channel.
Free kick awarded for a foul by Clint Hill on Danny Welbeck. Nemanja Vidic restarts play with the free kick.
Ashley Young takes a shot. Rio Ferdinand gets a block in.
Javier Hernandez takes a shot. Save made by Soares Julio Cesar.
Jose Bosingwa concedes a free kick for a foul on Ashley Young. Ryan Giggs takes the direct free kick.
Luis Nani takes a shot. Comfortable save by Soares Julio Cesar.
The referee gets the second half started.
Substitution (QPR) makes a substitution, with Jermaine Jenas coming on for Esteban Granero.
45:00 +2:14 Half time
Half Time The ref blows to end the first period.
Free kick awarded for an unfair challenge on Danny Welbeck by Stephane Mbia. Direct free kick taken by Ryan Giggs.
A cross is delivered by Ryan Giggs, Nemanja Vidic has a headed effort at goal from close range which goes wide of the left-hand upright.
Substitution Danny Welbeck on for Robin van Persie.
Javier Hernandez fouled by Clint Hill, the ref awards a free kick.
Effort from 12 yards by Robin van Persie. Save by Soares Julio Cesar. Corner from right by-line taken by Robin van Persie.
Drilled left-footed shot by Andros Townsend. Rafael Da Silva gets a block in. Outswinging corner taken from the right by-line by Esteban Granero, Christopher Samba takes a shot. Blocked by Rafael Da Silva.
Adel Taarabt has an effort at goal from outside the penalty box missing to the wide right of the target.
Andros Townsend takes a shot from a long way out clearing the bar.
Ryan Giggs concedes a free kick for a foul on Christopher Samba. Stephane Mbia takes the free kick.
Inswinging corner taken from the left by-line by Ashley Young.
Shot from just outside the box by Jamie Mackie misses to the right of the target.
Assist on the goal came from Robin van Persie.
22:44 Goal scored
Goal! - Rafael Da Silva - QPR 0 - 1 Man Utd Rafael Da Silva scores a goal from outside the area to the top left corner of the goal. QPR 0-1 Man Utd.
Bobby Zamora concedes a free kick for a foul on Nemanja Vidic. David De Gea takes the free kick.
Esteban Granero has shot on goal from just outside the area which goes wide of the right-hand upright.
Javier Hernandez is ruled offside. Indirect free kick taken by Soares Julio Cesar.
Inswinging corner taken left-footed by Robin van Persie from the right by-line to the near post, Armand Traore makes a clearance.
Javier Hernandez takes a shot. Save made by Soares Julio Cesar.
Adel Taarabt has an effort at goal from outside the area which goes wide right of the goal.
Free kick awarded for an unfair challenge on Michael Carrick by Bobby Zamora. Nemanja Vidic takes the direct free kick.
Jose Bosingwa challenges Luis Nani unfairly and gives away a free kick. Centre by Ashley Young, Close range header by Luis Nani misses to the right of the goal.
Robin van Persie is caught offside. Soares Julio Cesar takes the free kick.
Jose Bosingwa fouled by Javier Hernandez, the ref awards a free kick. Jose Bosingwa takes the direct free kick.
Free kick awarded for an unfair challenge on Bobby Zamora by Nemanja Vidic. The free kick is swung in right-footed by Esteban Granero, Ryan Giggs makes a clearance.
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