I would soak the cases in some Dawn suds for a while before washing.

Use Citrasolve. It gets out set oil stains. I’ve been using it over a decade. Even keep a bottle in laundry room. Spray or dab, let sit and wash in machine.

Try liquid Awesome (from dollar store).Kinda looks like apple juice.Great on my DHS pillow cases.

Then there is always plain old ammonia. It works at removing oil. Don't mix with Chlorine bleach though.

I wonder if the stains are not body oils but s from skin care products. I once used a la Roche Posay moisturizer that left oily looking stains on my pillowcase that refused to come out.

That's funny!

This week's attempt at removal is pre-treating with Tide Plus Bleach Alternative liquid.

Cavimum, I thought it might be skin care products, but it happens even when I only wash with Cetaphil cleanser at night and don't use moisturizer/other products. Go figure.

Tide plus bleach alt is fine to pretreat. No bleach in it.

For dh's pillowcases (with heavy oils), if I use hot wash, Borax and Mexican Ariel powder and a soak of 30mins minimum, this issue is resolved. He doesn't use any moisturizers though, he's just oily.

Verdict: the pre-treating and pillow case only wash did a good job, but not perfect. Sounds like I am getting closer!

For what it is worth, Ammonia does great for removing body oil and odor in hockey equipment.

I always use baking soda and white vinegar in every wash. It cleans, boosts detergent and gets rid of odors and oils.

Update 2: I pre-treated with Ecover stain remover, did a delicate wash with just the pillow cases with cool water, and then did the whole sheet set in hot. That seemed to do the trick. I'm having to do it every week because of the oils.

Well..as you know the stain is caused from a build up of oils that than turn like wax. I buy vintage, flat, white, 100% long staple cotton sheets from the 50's&60's....used....they are VERY stained and reek to the high heavens...I've had to boil them...but I also had good luck using Tide with Bleach powder and ammonia...but very very hot water is a must as is multiple hot soaks and washings....remove the oil build up and the stains will be gone...this is why I always say body oils can be the biggest soils..

And don't you go feeling bad...everyone has body oils no matter how often they shower. ..trick is if you have more body oils than the average bear...change your pillowcase more often..this will help prevent too much from clogging up the fibers.

I change mine and the boys daily..only takes a hot second and i have a lot of them

Good Luck.