The oil is diluting the grease to the point that it is thin enough to blow through the pipes, or put another way, the grease is thickening the oil enough to prevent it from reaching the engine. With the factory valve, there being no grease, most of the oil will reach the engine or collect in low spots in the charge pipes.
In a perfect world the oil could be used to lubricate the valves but there are too many contaminants for that to work. This is why we recommend that the valves be serviced periodically.
Eventual, after many heat cycles, the oil that has collected will turn to sludge where it has collected in large amounts and will yellow and turn into something akin to varnish on the surfaces with smaller accumulations. The intake valves and valve-seats will be coated with varnish and cruddy deposits. Catch-cans are a good idea if engineered properly.
