The Holywood golfer opened his round with a bogey, but he didn't let that get to him and went on to record three birdies and two eagles on the 16th and the 18th.
Two more bogies on the 12th and the 17th ensured a round of four under for the day.
The 25-year-old has set the pace on the championship and goes into Sunday's final round on 16 under, an impressive six shot lead over nearest rival Rickie Fowler.
He also set a new 54-hole record at Hoylake, his total of 200 beating the previous record by three.
The chasing pack may have little hope of catching the current world number eight, who is looking to secure the third leg of a career grand slam having already won the US Open and US PGA, but McIlroy said he was not getting carried away.
"I've won from seven back this year so I know how leads can go very quickly and I'm not taking anything for granted," he said.
"If the guys in front of me had finished a little better, finished the way I did, then my lead wouldn't have been as much as it was.
"Instead of a six-shot lead it could have been a one or two-shot lead.
"A lot can happen and I've been on the right side of it and I've been on the wrong side of it, that's why you can't let yourself think about winning, you've just got to completely stay in the present and that's what I'm going to try to do for all 18 holes tomorrow."
McIlroy looked happy and relaxed during his post-round press conference and while the Claret Jug is effectively his to lose those sort of thoughts are not entering his head.
"This is the third night in a row that I'll sleep on the lead. I feel very comfortable leading the tournament," added the Northern Irishman, who pledged to maintain his routine of going to the gym, eating and then settling down to watch a film.
"It helps that I've been in this position before and I've been able to get the job done.
I think whenever you have such a big lead you really can't think about anyone else but yourself.
"You have to think about how you're going to control your emotions, control whatever thoughts you have and focus on what you need to do."
His focus could not be questioned midway through his third round when it seemed his cloak of invincibility was slipping.
"I knew Rickie was playing well in front and then I saw on 12 he got to within one of me and then I bogeyed the hole and it was tied," he said.
"But I never panicked. I didn't feel uncomfortable. I knew I had some holes coming up I could take advantage of and make some birdies.
"I was just very patient and waited for my chances and I was able to convert those.
"I was conscious that Rickie was getting a little closer or Sergio (Garcia) but it was nice to be able to come up with the goods when I needed them the last few holes."
Should McIlroy lift the title on Sunday he will be three-quarters of the way to a career grand slam.
He added: "It would mean a lot of hype going into Augusta next year.
"I'd be in pretty illustrious company. I didn't think that I'd even have the chance at 25 to go for three legs of the Grand Slam so I'm going to try to put all of that out of my head.
"It would be way too much to think about. First things first, just play a good solid round of golf tomorrow and if that means that I'm going to Augusta next year with a bit of hype, then so be it."
Not a lot of people have achieved the career grand slam and if everything goes the right way tomorrow to get to three-quarters of the way there is some achievement by the age of 25.
Elsewhere, Darren Clarke also had a great round finishing in tied twelfth on five under par after carding a 67 for the day.
Clarke, who lifted the famous Claret Jug at Sandwich in 2011, said his new fitness regime helped him score his best round of the week.
He said: "I hoped it was the problem. If you've got 50 pounds or 60 pounds sitting in front of your gut you're going to swing a lot slower through the ball than what you would do otherwise.
"I kept leaving the club behind me but I've done a few things this week and the club's got back in front of me again so it's been better.
"The ball-striking has been pretty good. I just need to knock in a few putts and get some momentum going and it feels like I've started to do that."
Compatriot Graeme McDowell, who shot 68 to also be five under, questioned the R&A's decision to have a two-tee start because of possible bad weather.
"I was disappointed. Getting out a couple of hours in front of the leaders can often be an advantage," he said.
"The decision to play two tees looks interesting now. It is better to be safe and sorry but they were good, easy conditions out there from the point of scoring.
"The first three or four holes were very wet and nasty but the back nine was played in much more benign conditions."
The form of McIlroy, means McDowell, like many of those on the first page of the leaderboard, is playing for a consolation prize.
"It has given me a shot at something tomorrow but I'm not expecting the lead to be coming back in my direction," he added.
"A solid top-10 or top five all I can really hope for. Rory's two 66s would have been tough to live with the first two days but there is no doubt I'm ruing that two-over par on Thursday in probably the easiest conditions this week."