Preheat oven to 350 degrees F (175 degrees C). Grease 12 muffin cups or line with muffin liners.
In a large bowl, mix together the oil, sugar and vanilla. Beat in the eggs one at a time, then stir in the pumpkin.
Combine the flour, baking powder, baking soda, salt and cinnamon; stir into the pumpkin mixture.
Fill muffin cups two-thirds full with batter. Bake for 20 to 25 minutes in preheated oven. Muffins are done when toothpick inserted in center comes out clean.