How can I clean some really really nasty seats?

Search-engine pulled up these results:


There are number of upholstery cleaning agents available. Here I used a spray cleaner from Turtle Wax. Simply spray evenly on the seat or door upholstery and rub vigorously. Then, wipe it thoroughly with a dry cloth.
If you don't have a upholstery cleaner, simple laundry detergent will work as well. Just damp a rag with a little bit of water and the laundry detergent, squeeze the excess of water out and rub the fabric. Then, rub dry with a clean, soft cloth.
Don't soak the seat with water, it will cause stains on the seat and mould smell.


Link to website (http://www.samarins.com/maintenance/interior.html)

cloth or leather?

if they are leather use meguiars leather polish.If cloth you can find many products at your local part store i cant tell you the best product but i can say dont use anything turtlewax