Preheat oven to 350 degrees F (175 degrees C). Grease and flour two 9x5-inch loaf pans.
Beat vegetable oil and sugar together in a bowl until creamy and smooth; stir in eggs.
Mash bananas and lemon juice together in a separate bowl; mix into oil mixture until just incorporated.
Sift flour, baking powder, and salt together in a third bowl; slowly mix into wet mixture using an electric mixer on low until just incorporated. Fold in walnuts. Pour batter into the two prepared loaf pans.
Bake in the preheated oven until a knife inserted in the center of the loaf comes out clean, about 1 hour 15 minutes.
