Verified answer

Vehicles were never designed to "emit" oil to the ground either as a waste product or as a part of the motive process. You do have "breathers" on engines that can inadvertently leave a path for oil to get to the ground and you do have many vehicles that leak oil from one seal or another. With millions of vehicles on the roads the cumulative effect of a lot of leaks is an oil slick on roads that is apparent when it rains after a prolonged dry period.

Formerly improper disposal of drain oil has ushered in a certain amount of pollution as well.

Electric vehicles on the other hand do not need oil in their storage systems, motors, controllers or battery management systems. They don't need transmissions and can be designed with wheel motors so that they don't even need a differential. The drive train has few moving parts and these are permanently lubricated. Therefore they can be built with essentially no oil to leak or be disposed of improperly.

Cars do not emit oil, it is used as a cooling agent(motor). Spills and leaks can get to the Ocean via storm drains. The occasional oil spill on a barge or tanker occurs and is promptly cleaned up with very little damage. The Ocean is self cleaning to a degree with it's movement.

Ditto on the previous answers except - Where ever you have moving metal parts, you typically have a lubricant that is petrol-chemical based. And although many are sealed in contained systems, seals and contained systems do have the potential for failure; if not in operation, in an accident.

What all privately operated vehicles do have are tires - and, I think I'm safe in saying that all have petrochemical based tires. They do wear and are capable of measurable water way contaminates/pollution. And, they also have brakes that function using friction with the wearing away of brake material. Measurable water way, brake originating contaminates/pollution have also been found.

A gasget is loose.

Check these out..

http://www.youtube.com/watch?v=l-z-ztw69Ag

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http://www.youtube.com/watch?v=nmZTFxXbK-Y

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http://www.youtube.com/watch?v=SokvAZlHyIQ