Re: Engine oil stains on deck gelgoat
Maybe one of the "enzyme" laundry products that actually breaks down oil, or a similar bilge product. Build a little clay dam around it, fill it up, cover it with plastic, let it sit. Scrub, change the fluid, repeat in a day or two and see if it breaks the oil down enough to pull it out.
Masons do something similar to pull stains out of porous stone, they put a poultice of absorbent powder on top, dampen it, let it "pull" the stain out. You might be able to check that out.