Preheat oven to 180°C. Line a large loaf tin with baking paper.
In a large bowl combine oil, sugar, banana, eggs, vanilla and chocolate. Mix well.
Sift flour and baking powder into the wet ingredients. Combine gently, do not ove rmix.
Pour mixture into prepared loaf tin and cook for 1 hour or until a testing skewer comes out clean. Remove from the tin and allow to cool on a wire cooling rack.