Place in large bowl:

2 c. sugar
2 c. flour
1 tsp. baking soda

Combine in saucepan:

1 c. coca cola
1 stick butter
1/2 c. oil
4 tbsp. cocoa

Bring to boil. Remove from heat. Add 1 1/2 cup marshmallows. Stir to dissolve. Add 1/2 cup buttermilk.

2 eggs, beaten
1 tsp. vanilla extract

Add cooked mixture to flour mix, stir well. Pour into 9 x 13 inch pan. Bake at 325 degrees for 45 to 50 minutes. Frost with coca cola frosting while cake is warm.

COCA COLA FROSTING:

3 tbsp. cocoa
1 stick butter
6 tbsp. coca cola
1 tbsp. vanilla
1 box powder confectioners' sugar
1 c. chopped nuts (optional)

Combine first four ingredients in saucepan and bring to a boil. Remove from heat. Add powdered sugar and nuts. Beat until smooth. Spread on warm cake.