Johnson, coming off the back of a victory at the Northwestern World Challenge in December, produced a round of seven under par 66 on the par 73 layout.
The 37 year old is playing this event for the 7th occasion but until this week there has not been a lot to get excited about. He finished 6th in 2009 but that aside there have been no other top 15 finishes, his form this week perhaps reflecting a period where he is playing some of the best golf of his life, having also won the BMW in September and finished inside the top ten in eight of his last eleven starts.
The two Johnson's both recorded the rounds of the day (66) Dustin bouncing back from a setback early in his back nine to birdie three of the last five holes although by then the older Johnson had established such a lead he was always going to lead through 36 holes.
When asked after his round how the round compared to how he played, Johnson reminded the interviewer that he has not parred any of the par fives indicating that he felt it could have been even better.
Adam Scott added a second consecutive 70 to be at 6 under and seven shots from the lead.