Preheat oven to 400 degrees F (200 degrees C). Grease a 12-cup muffin pan, or line with muffin liners.
Combine flour, sugar, salt and baking powder. Place vegetable oil into a 2 cup measuring cup; add the egg and enough milk to fill the cup. Mix this with flour mixture. Fold in blueberries. Fill muffin cups right to the top.
To Make Crumb Topping: Mix together sugar, flour, butter, and cinnamon. Mix with fork, and sprinkle evenly over muffins before baking.