Manchester United may be lying in Arsenal's slipstream at the top of the table but they gained the high ground in the FA Cup.
Two goals from Darren Fletcher and one each from Wayne Rooney secured their place in the quarter-final.
Arsenal's cause was not helped, however, by Emmanuel Eboue's sending off in the 49th minute.
Both United boss Sir Alex Ferguson and his Arsenal counterpart Arsene Wenger made five changes with vital Champions League matches ahead next week.
It was Ferguson, however, who was left smiling after this rout of their title rivals.
United made a blistering start and it was no surprise they made the breakthrough in the 16th minute following a corner from Nani.
Anderson flicked the ball on and Rooney headed it beyond Jens Lehmann for his 11th goal of the season.
Three minutes later United made it 2-0 after good work by Nani on the left.
The Portuguese player chipped the ball into the area and Fletcher marked his first start in two months by heading home, although his effort seemed to take took a deflection off William Gallas.
It was all United at this stage with Arsenal looking lethargic and out of sorts.
Nani and Anderson were showing good skill while Rooney was bright after missing the derby defeat by Manchester City at the weekend after suspension.
He latched on to a pass from Patrice Evra in the 32nd minute, only to clip his effort wide of the post.
Fletcher then picked out Rooney two minutes later but he failed to test Lehmann from inside the penalty area.
However Wenger must have been alarmed at the amount of room the England striker was being given by the Gunners' defence.
United made it 3-0 in the 38th minute following a pinpoint pass from Michael Carrick from deep.
Nani was alert and skipped goal-side of Justin Hoyte to score with a low drive into the corner.
United started the second half where they had left off with Rooney testing Lehmann in the 47th minute.
A minute later the Arsenal goalkeeper had to look alert as a free-kick from Rooney spun off Fletcher.
Arsenal's problems increased in the 49th minute when they were reduced to 10 men.
Eboue was dismissed by referee Alan Wiley after a clumsy challenge left Evra on the floor.
Eboue refused to believe it and questioned the decision before being led away down the touchline.
United were spraying the ball around, particularly Carrick, and Arsenal were being constantly stretched.
Evra then picked out Nani inside the six-yard box after 58 minutes but his effort was safely taken by Lehmann.
While Lehmann was being kept busy, his opposite number Edwin van der Sar was having little to do.
Rooney could have extended United's lead in the space of a couple of minutes but each time his finish was wasteful.
Arsenal launched a rare counter-attack in the 64th minute but substitute Eduardo da Silva headed over the top following a cross from Cesc Fabregas.
Anderson then found himself in acres of space, only to toe-poke his effort wide of the target.
Rooney came off after 68 minutes and was applauded by England boss Fabio Capello.
Arsenal striker Emmanuel Adebayor was introduced in the 71st minute but three minutes later United made it 4-0.
Fletcher scored his second goal of the game with a header at the far post following a cross from the irrepressible Nani.
Adebayor joined Eduardo and Gilberto in the book soon after with United well on top and Nani beginning to showboat - much to the delight of the home fans.
However he took exception to the way he was being marked and squared up to Gallas.
United could have added to their tally but this was a super show nonetheless which secured their place in the last eight.
