1. Preheat oven to 400º.
2. Grease or line muffin tins.
3. Mix flour, sugar, salt, and baking powder.
4. Mix vegetable oil, egg, and milk, then combine with dry ingredients.
5. Fold in the blueberries.
6. Pour into muffin tins, filling to the top.
7. Make the streusel by mixing all four ingredients in a food processor until course, or by mixing the dry ingredients then cutting in the butter with two table knives. Sprinkle over on the muffin batter.
8. Bake 20 minutes.