There are many good products on the market today, many of us old timers and lots of car guys still use the old D&L hand cleaner with lanolin. It will take off grease and stains that are not permanent and leaves the vinyl very soft due to the lanolin. Look around at car guys who have older cars with vinyl roofs, many still use the D&L to keep those old roofs in good condition. That's about all I use or have ever used and never had an issue with dry or cracked vinyl no matter how old. Can be tuff to find at times but well worth the effort.
