I used to have quite a headache when I had to get rid of bike grease stains from my clothes every time I serviced my bike. I have read several tutorials for removing grease from clothes. It has solved all my problems. This process includes: using dishwashing liquid, using laundry detergent, baking soda, or stain remover. For dishwashing liquid, you should put a small amount of solution on the yellowed clothes and then brush them clean, then rinse with cold water. As for washing powder, it is the opposite. It is advisable to pre-treat the fabric and then add detergent to wash it.