AAAhhhh, Winter travel. Last week I "unwinterized my Newmar MH in 20 degree temps. (It is a winter package) I ran the funace for 18 hours before we left so that I could put water in it, and fortunately it all worked out until we made our first stop in Tennessee. I noticed that there is a big soot stain around the furnace exhaust that was not there when we left. I took a rag and warm water and the stain did not even diminish a little bit. Does anyone have advice on what I can use to remove the stain without harming the gel coat? The furnace is running fine, a nice blue flame. The soot is not getting any worse and I see no smoke of any kind. We must have sucked up something on the road. However this black soot is marring my baby. Any suggestions?