Hi, we are driving a Chevy Traverse. I thought we may need extra mirrors, now, I don't think so. The Traverse has the factory blind spot mirrors built in both driver and passenger sides and because the MPG is quite narrow, I have not had any problem. I agree with Bighorn, the more you can see the better and safer you are on the road. Having said that, I am constantly checking my mirrors when on the road and at this point I feel comfortable with the setup without any mirror ad ons.
In the interest of your own safety, if you are not sure and feel the Mountaineer is not giving you good vision, additional mirrors may be required.
Happy camping.
/