Gerry sent me this link to an article from GreenCar. The 3,000 Mile Oil Change Myth states:
"Using 2005 data, the [California Integrated Waste Management] Board estimates that Californians alone generate about 153.5 million gallons of waste oil annually, of which only about 60 percent is recycled. Used motor oil poses the greatest environmental risk of all automotive fluids because it is insoluble, persistent, and contains heavy metal and toxic chemicals. One gallon of used oil can foul the taste of one million gallons of water."