Step 1: Preheat oven to 400 degrees F (200 degrees C). Grease muffin cups or line with muffin liners. Step 2: Combine 1 1/2 cups flour, 3/4 cup sugar, salt and baking powder. Place vegetable oil into a 1 cup measuring cup; add the egg and add enough milk to reach the 1-cup mark. Mix this with flour mixture. Fold in blueberries. Fill muffin cups right to the top, and sprinkle with crumb topping mixture. Step 3: To Make Crumb Topping: Mix together 1/2 cup sugar, 1/3 cup flour, 1/4 cup butter, and 1 1/2 teaspoons cinnamon. Mix with fork, and sprinkle over muffins before baking. Step 4: Bake for 20 to 25 minutes in the preheated oven, or until done.