Byron, who had not finished better than 14th in the past five races, left little doubt in Sunday’s race, leading 66 of the 90 laps.
Byron cycled to the lead following a caution early in the final stage for Chase Elliott’s stalled car and cruised to a 2.632-second win over Denny Hamlin, who started on the pole.
The victory is a series-leading fifth for Byron, who drives the No. 24 Chevrolet for Hendrick Motorsports, and ninth of his career. It’s also the first road course victory in the Cup series.
Byron burnout. @WilliamByron | @TeamHendrick pic.twitter.com/zQJIbKRc8s
— Xfinity Racing (@XfinityRacing) August 20, 2023
Christopher Bell ended up third, A.J. Allmendinger was fourth and Ty Gibbs rounded out the top five.
Completing the top-10 were Martin Truex Jr., Chris Buescher, Tyler Reddick, Ryan Blaney and Joey Logano.
After the race, NASCAR confirmed both Kevin Harvick and Brad Keselowski had clinched a spot in the 16-driver playoff field.
Next Saturday night’s race at Daytona International Speedway is the final race in which a driver can win his way into the playoffs.
"You know, just a huge credit to the race team behind me. I want to thank Max Papis. This first road course win - we've worked years and years for this," Byron said. "Thanks to him. I know he's watching back home.
"I think it shows that when we're at our best, we can perform like this. We seem to go through that summer slump in July and August, and for some reason we just can't quite put the races together. I think it's the race tracks itself.
"We just came this weekend with a good mindset, focusing on trying to get ready for the post-season, and we've had fast cars, we just haven't executed races, but today was flawless, and just Rudy (Fugle, crew chief), everybody, all the spotters. Thanks to everybody. This is a cool win. Road courses have been tough, so it's fun to get a win."
Stage 1
Upon completion of lap 20, Michael McDowell led Byron by 0.821 seconds and claimed the Stage 1 win. Hamlin was third, Gibbs fourth and Allmendinger rounded out the top five.
Daniel Suarez spun in the exit of the bus stop and hit the guard rail with the nose of his No. 99 Chevrolet on lap 5 but was able to continue in the race.
Several cars elected to make a green flag stop prior to the end of the stage, including Blaney, Truex, Chase Elliott, Logano and Austin Cindric.
Stage 2
Upon completion of lap 40, Byron led Hamlin by 0.730 seconds and was awarded the Stage 2 victory. Gibbs was third, Kyle Larson fourth and Allmendinger had moved up to fifth.
While making his first green flag stop of the race on lap 21, McDowell beat Hamlin off pit road but was penalized for driving through too many pit boxes on entry. After his penalty, he dropped to 17th in the running order.
Big penalty for stage one winner Michael McDowell for driving through too many pit boxes. pic.twitter.com/h0qF9uaz1W
— Xfinity Racing (@XfinityRacing) August 20, 2023
Stage 3
Byron maintained a small but steady lead over Hamlin as the final 50-lap stage got under way.
With just under 40 laps remaining, Byron had built a more than five-second lead over Hamlin while Larson had moved into third.
Gibbs and McDowell kicked off a final round of green flag pit stops on lap 53 but Elliott ran out of fuel and his No. 9 Chevrolet came to a stop in the inner loop which forced NASCAR to throw a caution three laps later.
CHASE ELLIOTT RUNS OUT OF FUEL!
— NASCAR on NBC (@NASCARonNBC) August 20, 2023
It's looking like he MUST WIN at Daytona to make the playoffs. #NASCAR pic.twitter.com/73VuaqK2pN
Also, during the caution, the No. 23 Toyota of Bubba Wallace came to a stop with a fuel pick-up issue but did make it back to pit road.
During their respective pit stops, both McDowell – crew member over the wall too soon – and Larson – too fast on pit road – were assessed drive through penalties.
When the race returned to green with 30 laps to go, Byron led the way followed by Hamlin, Bell, Allmendinger and Gibbs.
With 15 laps to go, McDowell – who won last weekend’s race at the Indy Road Course – fell off the pace with an engine issue but was able to coast back to pit road. He eventually took his No. 34 Ford to the garage.
Byron maintained a two-second lead over Hamlin with five laps remaining with Hamlin’s teammate, Bell, close behind him in third.
