I bought a 5 year old boat this past summer, and while it was kept up very well, the grain in the vinyl was etched with dirt.  Soap and scrubbing wouldn't get it out... but this did.  A 30 second soak and a little scrubbing with a dish sponge and it looks brand new.  The white and grey vinyl has a completely different color now, new.  I will be using this product on my winter detail annually.