Preheat oven to 400 degrees. Grease muffins cups or line with muffin liners.
Combine flour, suggar, salt, and baking powder. Place vegetable oil into a one-cup measuring cup. Add the egg and enough milk to fill the cup. Mix this with flour mixture. Fold in blueberries. Fill muffin cups 2/3 full.
To make crumb topping: Mix together flour, sugar, cinnamon and butter. Mix with a fork and sprinkle over muffins before baking.
Bake for 20-25 minutes or until toothpick inserted in the center comes out clean. Freezes well.
