I have a tan leather couch that my 95 pound lab occupies. Over time he has managed to grind in black mulch, body oils, ect. The previous maid dutifully kept it clean using leather cleaner but subsequent maids were not so diligent. Now it is extremely dirty and the black mulch has ben ground in. I doubt it can be restored like new but what is the best way to try and clean it. I might add that ordinary leather cleaner is now ineffective.

Thanks to all who can offer advice. It is a very nice couch and I hate to replace it.