Done a suite today that hadnt been cleaned since brought new in the early eightys, so over twenty years old
Didnt look to bad at first but when i got to the contact areas it was caked full of what i can only discibe as blacktop the sort of thing you expect on a pub carpet.
Treated it as i allways do with Alltecs fabric pre-wash agitated and extracted, cleaned up ok on most of it but didnt even touch the head area and arms. So repeated this process another three or four times, still hadnt touched it wich suprised me as i have allways found this stuff really good.
So what do i do know im thinking

iv agitated and extracted several times what else is there

So i thought i would try something, Impact chemicalls (paint-oil-grease remover) as supplied by Woodbridge
Sprayed a bit on a towell and wiped over, this stuff just melted straight through the dirt and was bringing thick chunks of mud of at a time.
So i sprayed all the contact areas with it and aggitated and wiped of with a terry towell, ended up with six towells of thick black gunk, and that was after the first couple cleans. One last extraction and it looked like new i couldnt belive it

Not a conventional chemicall for suites to my knowledge and somthing i have never tried before myself, but will def be doing again and a good chem to have on your van just in case you ever come across something really dirty.
This is now my favorite chemicall by far, it does what it says it does on the bottle every time without fail, and so much more.