Regardless of the engine mechanism, all power plants
used in the US must meet certain emission limits (now
and in the future) specified by the US EPA. It is ill
advised to incorporate lubrication into the inlet air
stream, or anywhere else, to lubricate the moving
components, as has been the approach for many rotary
designs. The requirement for future emission levels may
establish that the lubrication system of all engines,
including conventional piston engines, be designed to
minimize oil entry into the combustion chamber