Fathauer takes over at the top
Russell Knox, coming off his first win last week in Shanghai at the HSBC Champions, also made bogey on the last hole for a 65.
Harold Varner III and Si Woo Kim are just two strokes off the pace and now tied for third.
Park had a 10-under 206 total at Club de Golf Mexico, where she struggled with distance control in the high altitude the first two days.
Northern Irishman McDowell made seven birdies in an eight-hole stretch in his round of eight under to be 12-under-par for the tournament and one shot clear of America Derek Fathauer.
The 29-year-old carded a bogey-free, five-under 66 to move one shot ahead of compatriot Jason Bohn (65). “Like I say, been seeing it well and I’ve been knocking a few in, and that was a nice way to kind of finish the day with a couple birdies”.
Fathauer, trying to make it six straight PGA Tour events with a first-time victor, had a one-shot lead starting the final round but had only one birdie against two bogeys to fall back.
Leonard hasn’t had a top 10 in almost two years and has said he is trimming is schedule this year to spend more time with his wife and four children.
Play was suspended for around 75 minutes due to wind and rain, and then darkness brought an early end to play with 21 players unable to complete their rounds. The confidence he gained from outlasting a strong field has been on display this week, where he is 18 under for his last 48 holes following an opening-round 70.
The only thing that stalled McDowell’s big birdie run was the opening hole, where a poor approach led to bogey.
Lopez had a hole-in-one on the 174-yard fifth hole with a 7-iron.
An Byeong-hun (66) of South Korea, Sergio Garcia (67) of Spain and Lucas Bjerregaard (70) of Denmark were tied for second place.
The event was the third of four in the European Tour’s Finals Series.