In a large bowl, cream together the butter, vegetable oil, white sugar, brown sugar and confectioners' sugar until smooth. Beat in the eggs one at a time, then stir in the vanilla. Combine the flour, baking soda, cream of tartar and salt; stir into the creamed mixture. Mix in the pecans. Roll dough logs, freeze, cut into slices. Place the cookies 2 inches apart onto cookie sheets with parchment paper.
Bake for 10 to 12 minutes in the preheated oven, or until the edges are golden. Remove from cookie sheets to cool on wire racks.