D'oh indeed! I've oil stains on sleeves & cuffs, but not managed to grease the body. Still, now that it's lived-in, you can quit worrying about the size and just use it without concern.You might have to hope your medium fits OK - I went for a spin in the jacket this afternoon and I've noticed I managed to get a small oil stain from the chain on the front somehow DOH! Tried to clean it gently with fairy liquid but no joy..