A small amount of oil, if disposed of improperly, can contaminate large quantities of drinking water.
Car batteries contain lead and sulfuric acid.
The lead can contaminate the water and the acid can burn skin. Most automotive supplies are recyclable. Used motor oil turned into a collection center can be burned as fuel or re-refined for use as a lubricant. When a car battery is traded in the lead and chemicals in the battery can be recovered. Oil filters are drained and recycled.