Easy Streusel Coffee Cake

1 Box yellow cake mix
1 box vanilla instant pudding mix (4 serving)
1/3 Cup vegetable oil
4 eggs
1 Cup sour cream
Beat yellow cake mix, instant vanilla pudding mix, oil, eggs and sour cream together until no lumps.
Grease and flour a bundt pan. Put 1/2 of the batter in pan. Sprinkle 2/3 of streusel mix over batter and top streusel with remaining batter then the rest of the topping. Bake at 350 for 50 minutes.
Streusel:
1/2 Cup flour
1/2 Cup brown sugar
2 tsp cinnamon
2 tsp melted butter.