There are no door seals to keep the sills clean. I bought the GM mudflaps but have not put them on yet. Do they help? (answer only if you have installed them please). Anybody else notice how filty the sills get if you drive on a dirt road or snow? The outer seal at the rear door/wheel opening doesn't seem to do anything; that area gets packed with road sand (we use sand not salt in this part of MI).