1) Place a strainer over a large mixing bowl. Measure in the flour, baking powder, baking soda, salt, cocoa, and sugar. Sift/shake the dry ingredients through the strainer into a mixing bowl, to eliminate any lumps.
2) Add the butter and mix at low speed for 1 minute. With the mixer running, add the oil and continue mixing until the mixture looks like sand.
3) Combine the vanilla with the milk and coffee or water, and add all at once. Mix for 1 minute at low speed, stop and scrape the sides and bottom of the bowl, then mix for 30 seconds.
4) Add the eggs one at a time, beating well at medium-high speed between additions. The batter will be thin.
5) Pour the batter into the prepared pan of your choice (one 9" x 13" pan, two 9" round pans, or three 8" round pans). Bake in a preheated 350°F oven for 34 minutes for a 9" x 13" pan; 28 to 30 minutes for 9" layers; or 24 to 26 minutes for 8" layers. The cake is done when a toothpick inserted in the center comes out clean. Remove from the oven and cool on a rack before frosting.