The three-time defending champion easily pulled away from Jeff Gordon after a restart with three laps remaining to win the Pepsi 500 on Sunday at Auto Club Speedway.
The win was Johnson's fourth at the two-mile oval, a place he has used as a personal launching pad to the title the past two years.
Johnson dominated the second half of the race but had to sweat out a series of double-file restarts following a number of late-race collisions, including one that forced the race to be red-flagged for 22 minutes with six laps remaining.
Juan Pablo Montoya was third, his fourth straight top-5 finish. Mark Martin, who started the day with an 18-point lead over Johnson, finished fourth and now trails Johnson by 12 points heading into Saturday night's race at Charlotte.