Like Arsenal, Manchester United have 51 points from 22 matches, but have a superior goal difference of plus-33 compared to the London club's plus-26.Chelsea beat Tottenham Hotspur 2-0 to move on to 47 points from 22 games. With 16 matches to play, the top three have pulled clear of fourth-placed Liverpool, who lead a quartet of clubs including Everton, Aston Villa and Manchester City on 39 points.
All six United goals came in the second half, with Ronaldo and Tevez putting the Reds on their way to their 10th successive home league win against their mid-table opponents who sacked manager Sam Allardyce on Wednesday.
Ronaldo scored his second of the match, and his 50th league goal for the club, to complete a well-worked move after 70 minutes with Rio Ferdinand making it 4-0 five minutes from time.
Ronaldo made it 5-0 and Tevez added his second in stoppage time to make it 6-0 before Newcastle's Alan Smith was red-carded for protesting about Tevez's second goal that barely crossed the line after bouncing down off the bar.
Arsenal, who started the day in first place, were hopeful of making it 11 home league wins out of 12 this season against a Birmingham City team that last won at Arsenal in 1957.
Arsenal had the best possible start, going ahead with a 20th-minute penalty from Emmanuel Adebayor. Birmingham battled back for a draw thanks to Gary O'Connor's 47th minute header.
Across London at Stamford Bridge, Chelsea, unbeaten at home by Spurs since 1990 and also unbeaten in their last 73 home league matches, took control after 19 minutes when Brazilian defender Juliano Belletti scored with a 35-metre shot.
They wrapped up the points with a second from Shaun Wright-Phillips 10 minutes from time.
Nicolas Anelka, signed from Bolton Wanderers on Friday, made his debut as a 60th minute substitute and nearly scored when he hit the underside of the bar in the dying minutes.
Liverpool moved back into fourth place, albeit eight points behind Chelsea, when they scraped a 1-1 draw at Middlesbrough -- their fourth successive stalemate in league and cup.
Everton went above Manchester City into fifth place after beating them 1-0, with Joleon Lescott scoring the only goal.
Aston Villa beat Reading 3-1 and also climbed above City on goal difference.
There was no joy for the bottom two clubs, Fulham and Derby County, who both lost again.
Fulham took an early lead at West Ham through Simon Davies but the Hammers fought back to win with goals by Dean Ashton and Anton Ferdinand, leaving Fulham without a win in their last 28 league matches.
Bottom club Derby County gave debuts to four new players but lost 1-0 at home to manager Paul Jewell's former club Wigan Athletic to remain bottom with just seven points.