Sometimes, a favorite T-shirt is almost like an old friend, becoming softer and more comfortable as time goes by. However, oily substances such as suntan oil, cooking grease, butter, mayonnaise, automotive oil or oil-based cosmetics can create nasty stains that can render a T-shirt unwearable. Don't toss your T-shirt in the rag bag until you try simple stain-removal techniques. Take care of oily stains as soon as possible, as stains are easiest to remove if they are less than 24 hours old.
Work heavy-duty liquid detergent or liquid dish detergent into the oil stain. Do not dilute the detergent. Alternatively, spray the stain with an aerosol type laundry pretreatment spray.
Read the laundry care tag to determine if hot water is safe for your T-shirt. Launder the T-shirt using your regular laundry detergent and the hottest water suitable according to the tag.
Inspect the T-shirt carefully. If you still see the oil stain, repeat the steps, then check to be sure the stain is removed.
Wash the stained T-shirt in hot water, laundry detergent and bleach if other methods fail to remove the grease stain. Use chlorine bleach if the shirt is white. If the shirt is colored, use an oxygenated, color-safe bleach. Use the products strictly according to the recommendations on the container. Always mix detergent and bleach into the water before placing your shirt in the washing machine.
Dry the T-shirt using your normal drying method when the oil stain is no longer visible.