Preheat oven to 190 degrees C. Grease or line muffin pan.
In a large bowl, mix together the flour, white and brown sugars, salt and baking powder. Stir in oil, eggs and milk until well blended and very few lumps remain. Gently fold in blueberries being careful not to mash them. Fill muffin tins 2/3 full or slightly more for a larger muffin top.
For the crumb topping, mix together the flour, softened butter, cinnamon and brown sugar. Place a small amount on top of each muffin.
Bake muffins in the preheated oven for 20 to 30 minutes or until a wooden skewer pierced in the centre comes out clean and dry.