use laquer thinner

but just go easy

do a test spot first

I once had a problem with some nasty stains on my bench seat. I was taking 4 new tires for my 5th wheel to the storage at the river. Well dumbass me didnt put towels under them, and just laid them on the seat not thinking twice about it. Well when I pulled them out lo and behold, nasty stains all over them and my seat is white. It seems the oils iin the tires leached onto the upholstery. I tried everything, that was suggested to me, and I mean EVERYTHING, to no avail . Well, and this is dumb luck, my canopy that I keep over my boat while at home, basically rotted away. So the boat sat out in the sun all day for about 2 to 3 weeks, until I got a new canopy. Next thing you know the stains just faded away, and are gone    just my .02

maybe try a lil bit of wd-40? it removes glue and stuff, ive never done it on seats though... worth a shot maybe

Try orange hand cleaner with the grit in it. I've always had good luck with it.

denatured alchol

The Beav

home depot, lowes. Denatured Alcohol, its like mineral spirits.

cover it with vinyl paint

hell, autozone brake cleaner works on EVERYTHING For me, lol i used it to take the vinyl coating off my boat rims, and they shine like no tomorrow, and it took the grease out of my carpet, it took the old roll on bed liner in my engine compartment off, i would give it a try, spray it on a towel and rub the spot, soo how it works. BTW what caused the stain? i have a slight rust ring from when a 5 gallon container of VP sat on the seat

Well after everything else failing we went to the lake 2 times so far.   It's FADING  fading.....
I'll just see how it looks in a couple weeks.
Thank you all for your ideas, this stain just wouldn't quit 

Mr Clean magic erasers work great.