I suggest you try CRC Brakleen brake cleaner with a mildly abrasive scrub pad.

Wow, keep the ideas coming. Will try them all on my test piece and go from there.

You have to fight the "chick stuff" with chick stuff. Try nail polish remover. I had a spot I could not get out. The wife suggested nail polish remover and it worked! No damage to vinyl.

The bourbon should work. The more you drink the less you'll see.

Try using some Goop, i think Lowes sells it. The press and bindery people use it to remove the ink from their hands at the printing co. i worked at.

Jim

Nail polish remover is diluted and scented acetone. --- JP

When I was having a motor done for an old boat of mine, I had a notepad with a bunch of notes on it and left it ink side down on my back seat. Then I forgot about it and it got wet and left everything I wrote down stained into the seat. I tried everything like you but I ended up quitting and eventually the sun took it out. I don't know how but over time it should fade away.

Try Marine cleaner wax in circular motion. Have removed some large pen marks with this..

Rubbing alcohol will usually remove ink and permanent marker.

I,ve used RaceGlaze for scuff marks on the back seat, probably from someone wearing sandles or sneakers. It worked well. Dog's marks may have penetrated the pores of the vinyl. Worth a try though.

Dog, don't waste too much good bourbon!!