Place pecans and 1/4 cup butter in a baking pan. Bake at 350 degrees for 20-25 minutes or until toasted, stirring frequently; set aside.
CAKE: In a large bowl, cream 1/2 cup butter, vegetable oil and granulated sugar, until light and fluffy. Add eggs, one at a time, beating well after each addition. Stir in vanilla. In a separate bowl, combine the flour, baking powder and salt; add to the creamed mixture alternately with milk, beating well after each addition. Stir in 1 1/3 cups of toasted pecans.
Pour into three greased and floured 9-inch round cake pans. Bake at 350 degrees for 25-30 minutes or until a toothpick inserted near the center comes out clean. Cool for 10 minutes before removing from pans to wire racks to cool completely.
FROSTING: Cream butter and confectioners' sugar in a large bowl. Add milk and vanilla; beat until smooth. Stir in remaining toasted pecans. Spread frosting between layers and over top and sides of cake.