Preheat oven to 350˚F. Butter a loaf pan.
In a mixing bowl (or processor), mash browned bananas, oil, sugar, and milk together.
Add eggs and vanilla, and mix to combine.
In a measuring cup, stir together flour, baking soda, and baking powder.
Add the flour mixture to the banana mixture and stir until just combined.
Pour into buttered loaf pan and bake at 350˚F until brown on top and cooked through, about 1 hour.