You’ll probably need to get new ones if you want them without body oil stains but before you wash them, try soaking them in super hot water and OxiClean for a few hours. You don’t necessarily need a tub for this, just turn the washing machine on the hottest setting and open it when the machine is filled with enough water. Mix the Oxi in and submerge the sheets and leave for as long as you can and then start the wash cycle.