Recent advances in chemistry have produced modern water miscible oil paints that can be used with, and cleaned up in, water. These are still 'real' oil-paints in every sense of the meaning. Small alterations in the molecular structure of the oil creates this water miscible property.
A still-newer type of paint, heat-set oils, remain liquid until heated to 265-280 °F (130-138 °C) for about 15 minutes. Since the paint never dries otherwise, cleanup is not needed (except when one wants to use a different color and the same brush). Although not technically true oils (the medium is an unidentified "non-drying synthetic oily liquid, imbedded with a heat sensitive curing agent"), the paintings resemble oil paintings and are usually shown as oil paintings.
