Pistachio Cake

1 package white cake mix
3/4 C vegetable oil
1C lemon lime soda
3 large eggs
2 ( 3 oz.) packages instant pistachio pudding mix
2 envelopes whipped topping mix( I used Dream Whip)
1 C mix
Beat cake mix, oil, soda, eggs and 1 package pudding mix until smooth. Pour batter into a greased 9"X13" pan. Bake for 45 minutes, or until cake tests done in the middle. Cool completely. Beat Dream Whip, milk and last package pudding mix. Beat until stiff peaks form. Chill for at least 1 hour before spreading on cake. Frost cake and refrigerate any leftovers.