I can't believe no on mentioned cancer. Oil, and most automotive fluids are cancer causing. Used oil, like when you do an oil change, is a lot worse as it is full of all kinds on nasty stuff like hydrocarbons and heavy metals. It isnt about washing the stain off, it is about what is getting through your skin into your blood stream and organs. I always wear surgical latex or nitrile gloves when messing with stuff.
