Dixon sliced ahead of Power on lap 24, taking the benefit of his fresh set of alternate tyres, and went on to score a famous victory by managing his fuel saving to perfection.
Power started the race from the front row on his softer-compound rubber, and jumped ahead of poleman Felix Rosenqvist at the opening corner.
He extended a 6.5s lead only for Christian Rasmussen to cause the race’s sole caution and negate his advantage.
Dixon started eighth and thus only had one qualifying run on his alternate tyres, while Power used both his sets for extra push laps in the Fast Six session.
He felt that the tyre deficit was crucial to why he finished sixth, 15s behind Dixon, despite mirroring his pitstop strategy.
“We had an incredibly fast Verizon Chevy,” said Power. “Had a choice to take the yellow and take tyres and have massive fuel save and go hard [on tyre choice], but we made the most of what we had there.
“We didn't have any green [alternate] tyres to run in those fuel save stints, so we didn't have any defence against Dixon. Otherwise, it would have been fine to do exactly what he did.
“Disappointing with how far we started up, but still a top six. All you can do is maximise each day and move on to the next one.”
Power was the only driver in the top 12 to finish on used primary tyres, with seven including Dixon on scuffed alternates, three on new alternates (best-placed Marcus Ericsson in fifth), and one on new primaries (Kyle Kirkwood in seventh).
After the race, Power’s claim that he was penalised by his tyre availability was taken to task by podium finishers Colton Herta and Alex Palou.
“He did two runs on greens [in the] Fast Six,” asserted Palou, to which Herta jumped in: “It's his choice, right?”
Palou added: “I mean, we didn't because we wanted to use it in the race.
“I would like if we could have an extra thing for Fast Six. But it was his choice this time. I mean, he was not put into that position.”
Dixon also found time to spare a thought for Power in his post-race winners’ press conference.
“I don't know where the #12 car finished, but he was on the same strategy as us,” he said. “I'll see where he ended up.”
Watch: Round 3 - Long Beach: 6 Minute Highlights