When I was growing up, my mom had a laundry stain treatment that I haven't seen anyone else I know use. Searching a store's laundry aisle for it a few years ago, I came up empty-handed, so I asked her where she found it. "Sometimes it's in the automotive care aisle," she answered, and that is indeed where I spotted one of my favorite stain-treatments.
Goop, which has been around since 1949, and has absolutely nothing to do with Gwyneth Paltrow, is primarily sold as a hand cleaner. As a child who liked to climb trees, I can attest that it worked better than anything else for getting sap off my hands. I think many mechanics use it for cleaning grease and oil off of their hands, and since she paid for college by working in an auto factory, that may be how my mom discovered her laundry tip.
These days, I use Goop mainly as a pre-treatment for stains that I suspect are oil-based, or that have been through the washer once already and failed to come out. I just rub a bit into the stain, let it sit for at least half an hour, then throw it in the washer with the rest of the laundry load. It's not foolproof, but it has saved many stained garments I would have otherwise given up on.
Apparently it's even more versatile than I realized. According to one Amazon reviewer, you can, "Mix this with liquid blueing [sic] and it's a miracle worker for white horse tails and those impossible to get out hock stains. Makes the tail feel freshly conditioned as well."
Its use isn't limited to horses, either. Reviewer "cmoreno" recommends Goop as a cat shampoo, saying, "Believe it or not I bought it to wash my Persian cat. Suggested by many groomers. Persians are greasy kitties. It works better than cat products but she's still a bit greasy. Still happy and it cost less than specialty shampoos."
While I can only endorse this laundry tip for clothing stains and hand cleaning, if you have greasy or stained creatures of any sort, Goop might be worth a try.