After running into misfortunes in Race 17, Sy came roaring back, zooming from second to the last in the 14-car grid to claim second place behind round and overall winner Winslow.
Sy, who was slowed down by a busted left rear-end tire in Race 17, gained 15 points for finishing second, erasing an 11-point lead by Irish Ali Jackson and sealing second place overall with 203 points.
"Before the race I told myself that this would be my last race in F3 (Formula 3)," said Sy. "But I really wanted to show and prove to them that I can win even if I start from the last."
Winslow, 25, took the last lap, again in dominating fashion as he timed in 17 minutes and 48.511 seconds, or way ahead of Sy’s clocking of 18:05.888 to run away with the overall title with 282 points on eight wins, including six in Sentul, Indonesia and two in RP.
It was a big improvement from last year when Winslow bested Sy by just one point for third place.
Winslow will go home as the series’ sixth champion after Jojo Silverio in 2001, Mark Goddard in 2002, Pepon Marave in 2003, Aussie Christian Jones in 2004 and Indonesian sensation Ananda Mikola last year.
"It was exhausting but I’m happy, I was just better racing with all the pressure off,"said Winslow, a driving instructor in Silverstone Circuit back home.
"The plan is to win it on my second year and we did that, we achieved our goal. We took the title with two races to spare and I’m glad we came up with these wins," he added.
Jackson, who needed to just stay ahead of Sy to clinch second place, encountered engine trouble in the crucial race of the series.
Going into the race ahead of Sy at No. 2 after a podium finish in Race 17, Jackson stalled at the grid and was left by almost a lap by the rest of the pack including Sy, who quickly pounced on the opportunity.
Jackson settled for third overall with 200 points.
Dillon Battistini, also of Great Britain, finished fourth, more than 22 seconds behind Sy, in the series backed by PLDT myDSL, Yokohama, Big Shot Billiards, Mossimo, Oxy Enhanced Water, Lima City Hotel, Asti Cinzano, Samsung, Silver City Automall, Viva Mineral Water and Powerade.