Used oil is insoluble, persistent, and can contain toxic chemicals and heavy metals.
It's slow to degrade. It sticks to everything from beach sand to bird feathers. Used oil is a major source of oil pollution in our nation's waterways. Americans who change their own oil throw away 120 million gallons of recoverable motor oil by dumping it illegally. Recycling this oil would save the United States 1.3 million barrels of oil per day.