A friend and I were invited to participate in an article for Muscle Car Review that was covering proper care and preservation of older paint jobs that was held down at Meguiars in Costa Mesa, CA.  The writer of the article decided to include a section devoted to vinyl care since my 27 year old white vinyl top on my '67 GTO definitely needed some TLC.  I had tried various commercial products over the years without success, and had even tried Simple Green and Purple Power that also failed to really clean the top.  Mike, the Meguiars tech, worked a small area at a time with very little effort until he had expanded the cleaned area out to about a one foot square. That portion of vinyl literally looked like new.  Since this was for a magazine article, that's where they stopped after getting the necessary photos for the article.  Although I was a little worried (OK, very worried) that the remainder of roof might never equal what a professional had done, I arrived home and placed my Amazon order for the #39 cleaner along with other products they had used on my paint with excellent results.  Well, the cleaner arrived yesterday, and we finished cleaning the roof by doing a small section at a time and working the cleaner in with a brush and then wiping off the cleaner and dirt.  While it was a slow process, it was not tedious or hard work.  Our finished result looked every bit as good as the spot cleaned down at Meguiars, and we cannot tell where they started and we finished the cleaning - and we know where the two joined up.  We did use a full bottle on the roof, but it really had a lot of embedded dirt that had to be removed.  I'll see if I can't post up a picture where we cleaned up to the tape with the other side of the taped area not touched yet.  We also found that a short, soft bristled brush worked best in getting into the pockets and lifting out the dirt.  On a side note, the guys also tested out the #40 cleaner on the vinyl roof and it was just about half as effective cleaning the roof.  I'm ordering more bottles of the #39 and going after my vinyl seats next.