Does anybody else notice a black crud on their braided stainless lines...

At first I thought I had a leak but also noticed Ron (fishercat) seemed to have the same greesy crud we thought it might be road crud...but it only seems to form on the lines...

I cleaned it all off about a week or two ago and just noticed it's back..?????


THE VOICE OF REASON per: Stewart AF&AM/Shriner/Scoutmaster 130/45 TBS 2shim SS Uni 18/42