Preheat oven to 350 °F. Cream butter with oil and 2 cups of the sugar until blended. Add egg yolks one at a time, beating well after each addition.
Beat in hot water. Sift together flour, baking powder, baking soda, salt, nutmeg, cinnamon and allspice, beat into egg mixture. Stir carrots and walnuts.
Beat egg whites until frothy, then gradually add the remaining 1/2 cup sugar in four additions, beating until stiff peaks form. fold into batter.
Pour into a greased and lightly floured 9-inch tube pan. Bake 60 -70 minutes or until cake tester or toothpick inserted in center of the cake comes out clean.
Before removing cake from pan, pour half of the soaking syrup on cake, distributing evenly. Let cake cool completely. Turn out on serving platter and brush remaining syrup on cake.
Let strand in refrigerator one day before serving.