Tyler Reddick passed William Byron with five laps go, withstood a charge by Kyle Busch in three NASCAR overtimes, and won Sunday's EchoPark Automotive Grand Prix road course race in Austin, Texas.
After passing Byron's No. 24 Chevrolet in Turn 11 with five circuits remaining, Reddick's No. 45 Toyota led the field and beat Busch's No. 8 Chevy in three green-white-checker finishes for his first victory this season.
In winning the Cup Series' third annual event at the 3.41-mile, 20-turn Circuit of the Americas, Reddick recorded his fourth career victory - three coming on road courses (Road America, Indianapolis Road Course).
Busch came in second, followed by Alex Bowman, Ross Chastain and Byron.
Sports car specialist Jordan Taylor started the No. 9 Hendrick Motorsports Chevy in place of injured Chase Elliott and finished 24th.
Formula 1 champions Jenson Button (18th place) and Kimi Raikkonen (29th) made their season debuts.
Road racer Conor Daly finished 36th.
In his 400th career start, A.J. Allmendinger brought his No. 16 Chevy home in 34th.
By earning his ninth career top qualifying spot, Hendrick Motorsports' Byron paced the 39-car field to the start of the 68-lap race, which was debuting the use of NASCAR's new low-downforce package on a road course.
After an incident on Lap 11 involving Bubba Wallace, Kyle Larson and Denny Hamlin, Byron took the lead during the race's first caution period.
With NASCAR's new road-racing rule of not having cautions at its stages, Byron restarted at the point and earned the first segment's bonus points -- his fourth stage win thus far -- as the race restarted.
Reddick put his Camry back on the point as pit service cycled around and won Stage 2 by nearly eight seconds over Austin Dillon.
--Field Level Media