Preheat oven to 400 degrees. Grease 8 muffin cups or line with muffin liners.
Combine flour, sugar, salt and baking powder. place vegetable oil into a 1 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, and sprinkle with crumb topping mixture.
Make crumb topping: Use a fork to mix together sugar, flour, butter and cinnamon, then sprinkle over muffins before baking.
Bake for 20-25 minutes in the preheated oven, or until done.