Preheat your oven to 350°F (175°C) and line a muffin tin with paper liners.

In a large bowl, whisk together all-purpose flour, sugar, baking soda, baking powder, salt, cinnamon, nutmeg, ginger, and cloves.

In another bowl, mix vegetable oil, pumpkin puree, eggs, and vanilla extract until smooth.

Combine the wet mixture with the dry ingredients, stirring gently until just combined.

Fold in the chopped walnuts if using.

Divide the batter among the muffin cups, filling each about two-thirds full.

Bake for 20-25 minutes, or until a toothpick comes out clean and the tops are golden.

Allow muffins to cool in the pan for 10 minutes before transferring them to a wire rack.