Since we’ve been looking at some interesting engines lately that take the road less traveled, a comment by rafe03 on the Ellwood Hybrid story pointed to this hybrid that needs no oil in the crankcase and no oil pump either, but it operates as a 4 stroke. The fuel mix lubricates the engine like a 2 stroke.
The fuel mix is drawn in through the crankcase and, by a very roundabout way, makes its way to the intake port, lubricating everything along the way. There’s an animation on the Stihl site but I’m having a little problem understanding exactly what’s going on.
Their engine is pretty small and used on weed trimmer type equipment, I have no idea whether this would scale up and produce decent power but it is interesting.