Ways to deal with organic oil stains on washable clothing: — Pretreat the stain with dishwashing liquid, such as Dawn. Dishwashing liquid contains surfactants that emulsify oil into tiny droplets and lift them from the fibers, allowing them to be washed away in the laundry. When applying, add a little bit of dish soap — don't go haywire — and then tamp with a brush. Tamping means you tap the cloth a little. This helps get the liquid into the fibers. Alternatively, you can rub the liquid in with your fingers. Don't scrub the surface too aggressively with something like a stiff-wired brush because you can ruin the surface of the fabric. — You can also pretreat the stain with an enzymatic stain remover. Enzymes break stains apart, so they become smaller, more water‑soluble molecules that can be washed away. However, each type of enzyme is only effective for a specific type of stain. So when you apply a stain remover, you're relying on a mixture of enzymes and hoping something in there will be useful for your situation. For oil stains, look for enzymatic stain removers that contain lipase, which works well on natural fats and oils, such as those from food. Note that it does not work well with petroleum-based oils, such as what you'd get from working on your car. Zout's "Laundry Stain Remover" and Dad Mode's "Deep Stain Remover" both have lipase. — After pre-treating the stain, let it sit for an hour or so, then wash with liquid laundry detergent. You can repeat this process a few times. — If this doesn't work, soak the garment for a few hours in Oxiclean. This is an oxygen-based bleach that contains sodium percarbonate, which oxidizes organic stain molecules and breaks them apart. Unlike chlorine bleach, oxygen-based bleaches are safe on colors. It's basically like applying hydrogen peroxide. However, it's not safe on all fibers — fine on cotton, not good on silk. Check the labels before using. — If the garment is very important to you, it's always best to send the work to a professional. IMO, the two best dry-cleaners in the United States are Rave FabriCARE (in Arizona) and Jeeves NY (in New York). Both companies will take mail-ins. IMO, you should not do anything to the garment before sending it in, as there's a chance you could make the situation worse. Zachary at Jeeves also runs a great laundry account on Instagram, which you can find at the handle jeeves_ny. Note that different types of stains require different solutions. The above is only for organic oil-based stains on clothes you can throw into a wet wash. Blood, sweat, and other types of stains will have to be treated differently.