Preheat oven to 325°F (160°C).

Grease and flour two loaf pans.

In a large bowl, cream together the cooking oil and sugar until light and fluffy.

Beat in the eggs, one at a time, until well combined.

In a separate bowl, sift together the flour and soda.

Gradually add the dry ingredients to the wet ingredients, alternating with the sour cream, until just combined.

Stir in the vanilla and mashed bananas until evenly distributed.

Pour batter into the prepared loaf pans.

Bake for 1 hour and 15 minutes, or until a wooden skewer inserted into the center comes out clean.

Let cool in pans for 10 minutes before transferring to a wire rack to cool completely.