Preheat the oven to 350F degrees and position the oven rack in the middle of your oven.
In a large bowl sift together the flour, cocoa powder, baking soda and salt. Whisk together until evenly combined.
In a large bowl, beat the butter and sugar until fluffy.
Beat the oil, vanilla, vinegar and red food coloring into the butter mixture.
Beat the eggs into the butter mixture 1 at a time.
Add about 1/3 of the flour mixture into the butter mixture. Stir together using a rubber spatula. Add 1/2 of the buttermilk into the red batter. Whisk until smooth. Add in another 1/3 of the flour mixture and stir until smooth. Then add in the rest of the buttermilk and stir or whisk until smooth. Finally, add the rest of the flour mixture. Stir by hand using, then whisk as needed until there are no more lumps of flour.
Brush your bundt pan with pan release, ensuring to get into all the creases. Or generously grease and sprinkle with flour or sugar. (I always use pan release).
Pour the batter into the prepared pan, and bake for 45-55 minutes or until an inserted toothpick comes out clean.
Cool the cake in the bundt pan for at least 15 minutes, then invert onto a wire cooling rack and continue cooling.