World number 17 Graeme McDowell produced a sparkling nine-under 63 at the Arnold Palmer Invitational on Friday to grab a share of the early second-round lead with American Jason Dufner.

McDowell, the 2010 U.S. Open champion, was bogey-free on the Bay Hill course and notched seven birdies and an eagle at the par-five 16th.

His 63, one shy of the course record, was in marked contrast to last year at Palmer's venue when the Briton slumped to an ugly 80 in the opening round.

"My record has not been very good here the last few years but still I had the belief I could come and compete here if I got it all together," said McDowell after finishing with a nine-under total of 135.

"It is going to be a quality leaderboard and it's nice to be in the mix heading into the weekend," added the Northern Irishman.

Dufner, the joint overnight leader with South Korean Charlie Wi, returned a 69 to join McDowell on nine under.

Spain's Sergio Garcia also showed promising pre-U.S. Masters form when a 67 put him on 139 along with American Bubba Watson (70).

Former world number one Tiger Woods and Briton Justin Rose were among the late starters.