Oil stains on clothes usually means you'll be buying a replacement for your favorite shirt or pants. However, there is a way to effectively remove oil stains on clothes, from cooking oil to motor oil, without much effort. Unlike methods that use cornstarch or talc, you won't be creating another more difficult mess. With a stock of paper towels and about a 1/2 hour of effort you'll be ready-to-wear again.
Lay the stained article of clothing flat in front of you on a surface that will not be harmed by the oil. It's a good idea to lay some paper towels under the area to prevent the oil from getting on your work surface.
Saturate the stain with WD-40 and add several drops of Dawn liquid dish soap on top of this.
Blot the stain with paper towels until it has completely lifted. Never rub a stain. Only blot or you will only work it further into the fabric. You'll know when the oil stain is gone when the paper towel comes away from the area damp, but not discolored by oil. If need be, re-apply step 2 until the stain is gone.
Wash the clothing by itself with a mild laundry soap. Dry the clothing as normal.
To prevent oil stains in the future, use a fabric spray like Fluoroseal Plus to provide a stain-resistant layer to the fabric.
Test a small portion of the fabric with WD-40 to make sure it will not damage the fabric (as with silk) or cause discoloration that lasts after the fabric is dry. If it does, use only the Dawn liquid dish soap, you will have to repeat the process longer but the result will be the same.