How to Make Diesel from Used Motor Oil

Collect waste motor oil (WMO) in a black, aluminum container and leave it in the warm sun for a few days; the color and type of the container will help draw heat into the oil, without reaching boiling point. Oil should never reach the boiling point; it should reach just below the point where it's smoking. If the motor oil is boiling, it will make it difficult to filter and you will be left with excess tar and sludge.

Use an electric inline fuel pump purchased from an auto shop to filter the warm oil through a fuel injection filter. You can prevent the pump from collecting sludge by keeping the suction hose off the bottom of the container. Most pumps will have a built-in pre-filter. Filter the heated oil into a separate and clean container, removing any particles that may have seeped through.

Clean out the filter by back flushing it with gasoline. This will move along the filtering process by cleaning the oil. You can do this by setting the filter in reverse and pushing the suction hose into a pan filled with gas. A clean stream of liquid will circulate when this step is complete. Filter six or seven times to break the oil down to micron-sized units.

You can also use a condenser which will vaporize some of the oil. Too much condensation will result in the loss of diesel through vaporization, however, so use this step in moderation. Now you have successfully converted used motor oil into diesel.