Preheat oven to 400 degrees. Grease muffin cups or line with muffin liners. It makes 8 muffins.
Combine 1½ cups flour, ¾ cup sugar, salt, and baking powder and set aside.
Place vegetable oil into a 1 cup measuring cup; add the egg and enough milk to fill the cup. Mix with the flour mixture.
Fold in the blueberries and fill muffin cups right to the top.
To make crumb topping: mix together ½ cup sugar, ⅓ cup flour, ¼ cup butter and 1½ tspn cinnamon. Mix with a fork, and sprinkle over muffins before baking.
Bake for 20-25 minutes.
Recipe by A Frugal Chick at https://www.afrugalchick.com/cooking-for-one-recipes-blueberry-muffins/