Cake:
Add to a large mixing bowl: cake mix, ¾ cup oil, eggs, (1) can mandarin oranges with juice. Mix with mixer at medium speed for 3 minutes or until well blended. Transfer batter to greased and floured cake pan(s). Bake at 350 degrees for 30 minutes in two round cake pans or 35 minutes in a 13×9 inch pan. Remove from oven and cool completely.

Frosting:
Mix the pineapple with juice and pudding mix together. Let set for a few minutes until slightly thickened. Fold thawed whipped topping into pineapple/pudding mixture until well blended. Frost the cake and refrigerate until ready to serve.
If desired, before serving, drain a second can of mandarin oranges and use it to garnish or decorate the cake.