A little while back my friend that it would be hilarious to put masking tape all over my car and draw on the tape. After peeling it all off the tape left whatever they drew on it on my fenders, not anywhere else. I have used soap&water, and Mothers Back to Black to remove it but neither work, any solutions to this problem. The fenders are just black plastic if that makes any difference.
Say hello to Rustoleum BedLiner or Krylon Fusion. Get to know them well...they will be your new best friend. There are dozens of threads on this. Just depends on the look you want as to which to go with.
rustoleum krylon fusion. painted mine black. just mask around the fenders as taking them off is time consuming. ive also heard you can use a torch to get them black. not sure on how effective that is though.
I used Forever Black on mine, and it left streaks no matter what I did with it. I ended up going with bed liner, and they came out great.
I was able to get a good even finish, but it isn't nearly as durable as painting with Krylon Fusion or similar products. In full sun, it didn't last six months before I was looking to "refinish" the fender flare extensions again.
2000 4.0l Sport, Auto, some mods done - planning more
I use forever black on mine but it doesnt last very long especially after rain. I plan to paint mine down the road because using the forever black can be a pain when you have to coat it multiple times.
I work at a car wash and put armor all on mine keeps them black. Anytime a older jeep comes with flares that look like it hasn't been touched in years I'll put it on there and looks just like new. Just do it like once a month or every other month