Bruno Junqueira was third.
"We just did what we had to do," Wilson said. "With the car
working well, it was exciting to be out there."
Sebastien Bourdais' hopes of clinching a fourth straight title
were hampered after a poor start forced him to drop from pole position.
Bourdais, who finished seventh, still has a 58-point lead over Wilson heading into the next race on Oct. 21 in Surfers Paradise, Australia.
"It's just frustrating. It was a weird race, it never quite got going for us," said Bourdais, who won from the pole last weekend at Zolder.
Wilson overtook Bourdais on the first turn and kept his lead
through the first round of pit stops.
Heylen moved up to second after the third pit, behind Wilson,
who had opened up a six-second lead and was never caught.
Heylen put the frustrations of finishing 13th at his home
Belgian Grand Prix behind to come in second.
The Formula One-bound Bourdais had won at Long Beach, Houston, Portland, Edmonton and Elkhart Lake and Zolder this season.
Robert Doornbos, who needed a podium finish to boost his chances
of catching Bourdais in the standings, placed 13th.
"Obviously, I am disappointed by the result, but we still have
some chance in the next two races," the Dutchman said.
Champ Car president Steve Johnson pledged his commitment to the
series' success in Europe after promoters said the Zolder and Assen
races jointly attracted about 115,000 spectators,
"You have to like it here," Johnson said. "We will certainly be coming back because it's evident there is a lot of passion for the race."