Preheat oven to 350 degrees. Grease light colored loaf pan (8 1/2" x 4 1/2" x 2 3/4” high) with non-stick cooking spray and set aside.
In a large bowl, mix oil, butter and, sugar until well combined. Stir in eggs, vanilla and, pumpkin until smooth.
Gently stir in dry ingredients and buttermilk until it's uniform batter has formed. Scrape sides to ensure no lumps are present. Stir in 3/4 cup chocolate chips. Pour into prepared pan and top with remaining 1/4 cup chocolate chips.
Bake for 50 to 60 minutes in the lower half of the oven until completely baked. Remove from oven and cool at least 15 minutes before removing from pan. Slice and serve.