Seriously good blueberry muffins

I came across this recipe and oh yum, they are delicious!

INGREDIENTS
1 1/2 cups all-purpose flour
3/4 cup white sugar
1/2 teaspoon salt
2 teaspoons baking powder
1/3 cup vegetable oil
1 egg
1/3 cup milk
1 cup frozen blueberries

Optional: 1 tsp of cinnamon or lemon/orange zest
DIRECTIONS
1. Preheat oven to 400 degrees F (200 degrees C). Grease muffin cups or line with muffin liners.

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 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.

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.

4. Bake for 30-35 minutes in the preheated oven, or until done.