"It was very close," said Shwartzman. "I tried to catch Richard for a while, but then decided not to take any risks."
Brit Clement Novalak completed the podium while Kiwi Brendon Leitch was fourth.
Veteran driver Kenny Smith came home 13th in his first race in the series.
"I got a bit too aggressive half way through the race," said Smith, who had fallen off the back of a bunch dicing for places at the bottom of the top 10.
Sunday's action features a reverse order morning race before the Grand Prix in the afternoon, which serves as the championship finale.
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