Oxyclean is just powdered Hydrogen Peroxide- and if you're not careful it can eat holes in your clothes!
I'd recommend just rubbing in regular liquid detergent with an old toothbrush, letting sit for at least an hour, then soaking in cold water overnight. Wash, then check to see if the stains are still there BEFORE you put them in the dryer (so the stains won't set). If that doesn't work, take a shirt to a dry cleaner and see if they can get the stain out- if they can, take all your shirts there.
It's entirely possible that a bit of oil found its way into your washer somewhere along the line. I really don't know what to do about that... other than google it or call the company that made the washer and ask them what they'd recommend.
How's Boone
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Sage knows our mythic history, King Arthur's and Sir Caradoc's
She answers hard acrostics, has a pretty taste for paradox
She quotes in elegiacs all the crimes of Heliogabalus
In conics she can floor peculiarities parabolous
-C'hi