Austin Dillon passed Kyle Busch and Daniel Suarez on the final lap and surged to an improbable victory in the Xfinity Series race on Saturday.
Busch got within two miles of his record-tying fourth consecutive Xfinity win after leading 133 of the 150 laps, but the defending Sprint Cup Series champ got a flat tire while attempting to save fuel.
Suarez briefly went in front while Busch attempted to keep racing on the sparking flat wheel.
But when Suarez ran out of gas, Dillon roared up and stole his seventh career victory in his Richard Childress Racing Chevrolet.
Dillon scraped the wall on the final turn while getting around Busch, who made contact with Dillon.
Dillon only led one lap, setting a record for fewest laps led by a winner.
The win is another boost for Dillon, Childress' grandson. He will start Sunday's Sprint Cup Series race up front after claiming his second career pole, hoping to finish the weekend with his first career Cup win.
Busch finished second and Darrell Wallace Jr. moved up to third. Suarez, Busch's Joe Gibbs Racing teammate, was fourth.
Busch had won every Xfinity race he had entered this season in his Joe Gibbs Racing Toyota. He came agonizingly close to becoming the second driver in the series' history to win four straight, joining Sam Ard in 1983.
Instead, Busch couldn't claim his record 80th Xfinity win. He has still won six of the last 12 races on Fontana's weathered two-mile asphalt track, where he also won the Sprint Cup races in 2013 and 2014.
Busch was in control for most of the race. Yet he knew his fuel might barely last, and he worried even more when teammate Erik Jones ran out with three laps to go.
Busch started third behind pole-sitter Suarez and Jones, his JGR teammates. Busch went down on the apron by the opening lap and seized the lead on the fifth, dueling with Kyle Larson early on before Larson got a flat with 54 laps to go.
Until the end, Busch was the class of a field that included 15 drivers making their Fontana debuts.