Ingredients :

1 box Duncan Hines Butter Cake mix
1/2 cup Wesson oil
1 11- ounce can mandarin oranges
1/2 cup sugar
4 eggs
Icing
12 ounce tub of Cool Whip
small instant vanilla pudding mix
1 16 oz. can crushed pineapple

Steps :

Preheat oven to 350 degrees. Combine cake mix, oil, oranges with juice, sugar and eggs. Mix at medium speed for 2 minutes. Bake at 350 degrees in 3 greased, floured and lined with wax paper pans for about 20 minutes or until center of the cake bounces back when touched. Cool in the pans for 10 minutes. Remove from pans and cool completely on cooling racks.
Icing
Drain juice from pineapple and set aside (If the icing seems to be too thick you can use it to thin it out a bit).
Mix pineapple with the instant vanilla pudding. Stir in Cool Whip. Frost the cake according to these directions. Store the cake in the refrigerator. I think it is better the next day.