I think the cold water is the largest problem. Scalp oils, hair products, perspiration., etc., leave our pillowcases in a different state than the sheets, especially in summer.

I always wash bed linens in HOT water. Hot water dissolves oil, grease, etc. much better.

Winter won't leave as much perspiration and body oil (dry skin from heated home) so perhaps that is why your flannel pillowcases are in better shape.

Try a true HOT wash and see if that helps. It might take a few wash cycles, but you should see a difference.

You might try soaking them in a pan or sink in hot water with blue Dawn dish detergent before putting them in the washer. This might help remove the build up.

Thanks for the suggestions. It's regular Tide powder that I use, and a common thread of replies has been that I should be using hot water wash. So that I shall, and we'll see what happens.

I agree with everyone else here. Cotton sheets should be washed in hot water. It may take more than one wash to un-do years of cold water washing....

try soaking the items in Dawn detergent for a couple of hours, drain the water, add HOT water, and hand wash them (wear heavy rubber gloves so that you can stand the HOT water) for a bit, then rinse them thoroughly. put them in the washer with detergent of your choice (hot water) and add vinegar to the rinse cycle. Get back to me with results.