The motor oil from one oil change will contaminate gallons of drinking water if not properly disposed.

It's about one million gallons of drinking water.
The motor oil that excreted during oil change will enter our watering system through the sewer.
If this not handled, this oil will enter itself into our water source that we use for consumption and cause potential poisoning in the long run

The motor oil from one oil change will contaminate one million gallons of drinking water if not properly disposed of.

Explanation:

Only one quart of oil can contaminate up to a quarter million gallons of drinking water or cause an oil slick almost 2 acres in size. Motor oil is used as a lubricant in motor vehicle engines.
The Environmental Protection Agency (EPA) does not consider uncontaminated used motor oil a hazardous waste if it is recycled for use as a lubricant or a fuel. However, improperly disposed of motor oil can contaminate the soil and surface and drinking water.

Ibelieve this would be an obstacle.