Preheat oven to 450 degrees F. In a medium bowl stir together flour, sugar and salt. Using a pastry blender, cut in butter until mixture resembles fine crumbs. Add sour cream and oil; toss with a fork to combine. Gradually sprinkle with enough of the ice water to moisten, tossing gently. Gather pastry into a ball, kneading gently just until it holds together (pastry may appear crumbly). Form into a rectangle. Wrap in plastic wrap and chill 1 hour.