Blot the oil spot with paper towels. Whatever you do, only blot and don't rub. If you rub, you can make the stain worse.
Lay the clothing flat and cover the oil spot with cornmeal. Leave it sit for a few hours so the cornmeal can absorb the oil.
Shake off the clothing to remove the cornmeal. Drizzle some heavy-duty laundry detergent onto the stain. Use your fingers to work the detergent into the oil spot. Let it sit for five minutes.
Wash the clothing in the hottest water allowed for the fabric, along with the recommended amount of detergent. Check the garment after washing and before drying. If the stain is still there, treat it again with heavy-duty detergent and rewash. Just don't put the garment in the dryer until all of the oil is gone or you may set in the stain.