Preheat oven to 350 degrees then line a 12-cup muffin tin with liners and set aside.
Add oil, sugar, and applesauce to the bowl of a stand mixer, or a large mixing bowl if using a hand mixer, then beat until pale and smooth, 1 minute. Add eggs then mix until just combined. Add vanilla then mix until just combined.
In a separate bowl, whisk together flour, cinnamon, baking soda, baking powder, and salt then add to the wet ingredient in two batches, mixing until just combined before adding the second batch. Add apples then fold into the batter with a spatula.
Scoop 1/4 cup batter into each muffin tin liner then bake for 24-26 minutes or until a toothpick inserted into the center of a muffin comes out clean. Let cool in muffin tin for 10 minutes before transferring muffins to a cooling rack to cool completely. Store in an airtight container in the fridge or on the counter for 3-4 days.