In a large bowl, whisk together the flour, granulated sugar, baking powder, and salt.
In a separate bowl, whisk together the vegetable oil, egg, milk, and vanilla extract. Pour the wet ingredients into the dry ingredients and stir until just combined. A few small lumps are perfectly fine.
Gently fold in the fresh blueberries using a spatula, being careful not to crush them.
Divide the batter evenly among silicone muffin cups or ramekins, filling each about two-thirds full. Sprinkle the tops with coarse sugar.
Preheat the air fryer to 310°F (155°C) for 2 minutes.
Place the muffin cups in the air fryer basket. Air fry at 310°F for 12 to 14 minutes, until a toothpick inserted into the center comes out clean and the tops are golden and spring back when lightly pressed.
Remove the muffins and let them cool in the cups for 5 minutes before removing. Serve warm for the best flavor and texture.