Scott Dixon took another big step toward a second IndyCar championship Saturday, holding off Helio Castroneves, his closest pursuer, for a victory in the Rexall Edmonton Indy.

Castroneves, still looking for his first win of the season, kept the pressure on Dixon lap after lap on the temporary airport circuit. But Castroneves nearly slid off course on worn out tires six laps from the end, allowing the New Zealander to cruise to his fifth victory of the season.