Preheat oven to 425°. Add 2 tsp. vegetable oil to a 10-inch cast-iron skillet; heat in oven 5 minutes. Stir together cornmeal mix and sugar in a large bowl. Add buttermilk, egg, and 1/4 cup vegetable oil, stirring just until blended. Pour batter into hot skillet. Bake 20 to 22 minutes or until golden and cornbread pulls away from sides.