I don't understand that last comment. ANY positive displacement pump oils by rpm. The flow out of the pump is directly proportional to the pump speed, which is directly proportional to crankshaft speed. EVERY engine wet sump oil pump is a positive displacement pump. I believe all of the dry sump pumps are as well. It could be possible to use a centrifugal pump, but operating characteristics of a centrifugal pump don't match engine lubrication needs very well.

I do not understand why you would say that a Melling pump would be all done by 3000 rpm. Melling makes most of the oil pumps that are sold for the US market. There is nothing about the design of a Melling pump, or any engine oil pump of which I am aware, that would make that happen.

On the other hand, if the oil pickup tube is constricted, or if the oil gets all foamy above 3000 rpm, then something like what I think you are describing is possible, due to cavitation.

R.