"I've done a majority of my scoring this week on the back nine and that's the way it went today," McIlroy said. "Took me a few holes to adjust. But once I got comfortable, I started to hit some good shots and give myself opportunities for birdies."
Donald had his third consecutive bogey-free round and has now gone 100 holes at the Dubai tournament without one. If he wins Sunday without carding a bogey, he will match the feat of Sweden's Jesper Parnevik, who won the 1995 Scandinavian Masters without dropping a shot.
"I was, again, just trying to play solid golf, minimize mistakes," said Donald, who won in Japan last week to overtake Tiger Woods for the No. 2 spot in the rankings. "I guess it's a testament to how I play the game. I kind of keep the ball in front of me and, when I get in trouble, I've got a good short game to bail myself out."
South Africans Louis Oosthuizen (68) and Charl Schwartzel (67) are three shots back, while compatriot Branden Grace and Joostis Luiten of France are a further two shots behind. Seven others are six shots off the pace, including Scotsman Marc Warren, who started the day tied with McIlroy and Donald but had three bogeys on his first 12 holes to fall out of contention.
Dubai World Championship
Luke Donald -17
Rory McIlroy -17
Louis Oosthuizen -14
Charl Schwartzel -14