Kyle Busch capably blocked Larson and outlasted Stewart and Kurt Busch to win a wacky race featuring a track-record 35 lead changes and numerous tire problems. With his 29th career Sprint Cup victory in his Joe Gibbs Racing Toyota, Kyle Busch is NASCAR's fifth winner in five races already this season.
"Holy cow, what do you expect when you've got a green-white-checkered finish and everybody has to come down pit road and put four tires on?" Busch asked after his third career win at Fontana. "That was 'Days of Thunder' right there. Unbelievable day."
Jimmie Johnson was comfortably in front when he blew a tire with seven laps left, precipitating the wild finish. Jeff Gordon moved in front until Clint Bowyer spun with two laps to go, setting up an overtime finish.
Gordon was hoping to finish on old tires when Bowyer spun, but then elected to pit along with most of the leaders. Kurt Busch gambled with just two tires, allowing him to restart in second, but his younger brother came up from fifth in the final two laps to win.
"I came off the fourth turn in disbelief that we won this thing, because we were mediocre all day," Kyle Busch said. "It was really weird for us, not a race that we're typically used to. But now there's a load off your shoulders that you can go out the rest of the season and race the way you want to."
He barely held off Larson, the 21-year-old rookie who held off Kyle Busch on Saturday to win the Nationwide race.
"I don't know where everybody went, but I somehow ended up in second and it entered my mind, 'We might sweep the weekend,' " Larson said.
He had to settle for the best finish of his Sprint Cup career in the No. 42 Chevrolet for Chip Ganassi Racing.
Kyle Busch, who went to Larson's car Saturday to congratulate him on his Nationwide win, pointed out his window at Larson after Sunday's finish, pumping his fist in approval.
"What a shoe that boy is," Kyle Busch said of Larson.
Several teams had serious tire problems on this weathered 2-mile oval, with multiple flats and cautions for various problems throughout the hot afternoon.
The problems likely were the latest effect of NASCAR's new aero rules, which are producing higher speeds that lead to extra stress on the tires -- particularly on the bumpy asphalt on Fontana's back straightaway, which already wears out tires aggressively.
Those problems might frustrate pit crews, but they can also lead to phenomenal racing, as the sellout crowd on its feet for the finish could attest.
"By no means is this a problem for Goodyear," Kurt Busch said, referring to NASCAR's tire manufacturer. "It's just a thumbs-up for NASCAR for allowing teams to get aggressive in all areas."
The intrigue and weirdness started early on at Fontana -- which somehow seemed appropriate for a race in which the Muppets' Gonzo told the drivers to start their engines.
Several drivers complained during an early pit stop that the red light was on, indicating pit road was closed. Gordon, Bowyer and Brad Keselowski did not pit because of the red light, and all were adamant NASCAR needed to correct their position in the running order.
It's the second consecutive week an issue with the caution light affected the race: At Bristol last Sunday, someone in the flagstand leaned on the button that turned the caution lights on right before Carl Edwards took the white flag. Rain then began to fall heavily, and the race could not be resumed, so Edwards won under caution.
Edwards finished 10th at Fontana and stayed one point ahead of Dale Earnhardt Jr., who finished 12th, for the overall points lead.
Hamlin was a last-minute scratch with a sinus infection, depriving him of the self-described chance for redemption after getting airlifted away from the track last year with a broken vertebra. Sam Hornish Jr. took his place in the No. 11 JGR Toyota and finished 17th.
Logano, in a backup car after a crash earlier in the week, had to go to the garage after 114 laps, knocking him out of contention. He finished 39th.