Dustin Johnson soared to a comprehensive five-stroke victory ahead of Rory McIlroy at the WGC-Mexico Championship.

American star Johnson claimed his 20th PGA Tour title following his final-round 66 at Club de Golf Chapultepec in Mexico on Sunday.

Now a lifetime member of the PGA Tour following his latest triumph, Johnson moved to second in the rankings and he will return to number one in the world the following week based on the two-year computations as neither he nor Justin Rose will play at the Honda Classic.

"I came here Monday – I struggled the last couple of weeks ... but I got here on Monday ... and it clicked," said Johnson, who extended his streak to 12 successive seasons with at least one win since turning professional in 2008.

Johnson – the only player to win every World Golf Championships event while he also joined Tiger Woods as the only other man to win a WGC tournament three times – was dominant, despite an early blemish.

The 2017 champion started on the front nine and bogeyed his third hole of the day but he recovered without dropping a shot, birdieing the sixth before the turn.

Johnson then managed back-to-back birdies from the 10th and he reeled off three in a row from the 14th to the 16th holes to seal victory at 21 under overall.

McIlroy tried to put a little pressure on Johnson but his four-under-par 67 was not enough to stop the red-hot American.

Four-time major champion McIlroy fired off five birdies in sevens holes on the back nine, however he was still trailing Johnson by five strokes.

Justin Thomas tied his own course record at Club de Golf Chapultepec with a low of nine-under 62.

American Thomas opened his round with three consecutive birdies and four in a row to start the back nine and carded 10 birdies in total as he finished in sole possession of ninth place at nine under, a stroke behind Sergio Garcia (70), Cameron Smith (70) and Patrick Cantlay (70).

Meanwhile, Woods capped off his weekend with another low round after shooting two-under-69.

Woods mostly kept his scorecard clean with just one blemish on the par-four eighth hole, rounding out the top 10 at eight under.