OAKMONT (AFP) -- World number two Rory McIlroy says his swing and driver struggles over the past month have improved as he prepares to challenge intimidating Oakmont in this week's 125th US Open.

McIlroy won the Masters in April to complete a career Grand Slam, a trek the 36-year-old from Northern Ireland began with his first major triumph at the 2011 US Open at Congressional.

The five-time major winner had his driver test non-conforming to golf rules before the PGA Championship and has struggled since to find a comfortable replacement, missing the cut in last week's Canadian Open.

"I feel a little better with the driver over the weekend at home and even today playing a practice round, so hopefully I can hit a few more fairways than I have been hitting and give myself some opportunities," McIlroy said Tuesday.

McIlroy had been testing several different drivers to find one that matched the feel of the familiar one he had worn down until it was done, and he was fighting swing issues.

"Hitting a lot of drivers. Every driver sort of has its own character and you're trying to manage the misses. It's definitely a little bit of both," he said.

"I think I learned a lot on Thursday and Friday last week and did a good bit of practice at home and feel like I'm in a better place with everything going into this week."

Asked what he learned, McIlroy replied, "I learned that I wasn't using the right driver."

McIlroy didn't have a top driver at the PGA Championship but noted that top-ranked Scottie Scheffler, the PGA winner, said after the win his driver had also failed a pre-event test.

"It wasn't a big deal for Scottie," McIlroy said. "So it shouldn't have been a big deal for me."

The big deal before him this week is one of golf's toughest tests at Oakmont, with dense rough, fast sloping greens and abundant bunkers.

McIlroy played a practice round last week at Oakmont and marveled at how tough the course played.

"You hit a ball off the fairway and you were looking for a good couple of minutes just to find it," McIlroy said. "It's very penal if you miss. Sometimes it's penal if you don't miss.

"The person with the most patience and the best attitude this week is the one that's going to win."

As for his round, McIlroy added: "I birdied the last two holes for 81. It didn't feel like I played that bad."

McIlroy starts off the 10th tee at 7:40 a.m. (1140 GMT) on Thursday alongside pal Shane Lowry, the 2019 British Open champion, and England's Justin Rose, the 2013 US Open winner.

- 'Can't relax this week' -

McIlroy has managed six consecutive top-10 US Open finishes, including a 2023 runner-up effort to winner Wyndham Clark and a second-place showing last year after his bogeys on three of the last four holes left Bryson DeChambeau the winner.

His US Open run coincided with a change in approach about the majors.

"I made the decision at that back end of 2018 into 2019, I wanted to try to build my game around the toughest tests that we have in the game," McIlroy said.

"The US Open went from probably my least favorite major to probably my favorite because of what it asks from you, and I love that challenge."

McIlroy won at Pebble Beach and the Players Championship before beating Rose in a playoff to make his green jacket breakthrough at Augusta National, a win he's still trying to get past.

"You dream about the final putt going in at the Masters, but you don't think about what comes next," McIlroy said.

"Chasing a certain goal for the better part of a decade and a half, I think I'm allowed a little bit of time to relax a little bit. But here at Oakmont, I certainly can't relax this week."