Wheel wells for car

Been trying to make a car model in blender and was wondering if anyone has any tips on the wheel wells, I have half the car (when all done just mirroring) and it's in more of a block form on the bottom so Im' cutting the wheel wells out with the boolean function and a cylinder. Problem is I'm trying to find a good balance of polygons and good looking wheel wells. Anyone have any tips for that or the best number of sides to use in a cylinder, so far I've tried up to 11 vertices and it's looking closer to being circular