MIAMI (AFP) - Australia's Jason Day stormed to a five-stroke lead during Friday's second round of the PGA Arnold Palmer Invitational after shooting a a bogey-free seven-under par 65 at Bay Hill.

Last year's PGA Championship winner has his eyes firmly set on back-to-back major titles with the Masters looming in only three weeks at Augusta National.

World number three Day birdied three par-5 holes and followed up his opening 66, which put him one stroke ahead when the round began, with another impressive round at the Orlando layout leaving him on 13-under 131 for 36 holes.

"It's great to be there," Day said. "Definitely way above average. I had it on a string around here the past two days. I'm very happy with the way I've gotten around this course."

Day, who began his round off the 10th tee, sank a two-foot birdie putt at the par-5 12th, tapped in for birdie at the par-5 16th after missing a 17-foot eagle bid and dropped a 37-foot birdie putt at the par-3 17th.

The Aussie dropped his approach inches from the cup to set up a birdie at the fourth, sank a 12-foot birdie putt at the fifth and added a three-footer for birdie at the par-5 sixth.

Then he closed out the round by banging in a 36-foot birdie putt at the ninth.

"My goal was to be patient out there but still aggressive with the lines I was taking," Day said.

"Today I hit some phenomenal drives to set up some great irons into the greens. Played the par-5s great and his a couple huge bombs out there."

American Jamie Lovemark was in the clubhouse a distant second on 136 after back-to-back 68s.