Pressure and volume are connected. If there is excess volume, pressure will rise. Low pressure indicates insufficient volume for the existing conditions. As RPMs increase the oil is wiped away from surfaces faster, so more volume is required. The way you get more volume is to increase pressure. That is why 10 pounds of pressure per 1000 RPM came to be the rule of thumb for oiling.
Well I guess that all the thousands of engines that were built without oil pumps and just used scoop and and splash oiling all exploded the first time they went over a thousand rpms, because I'm here to tell they didn't exhibit any measurable pressure at all when warmed up. Scott
Context is important. Many two strokes have no oil pressure either. Engines need to be oiled in the way they were designed, running a modern without proper oil pressure is the same as removing the scoops from a splash engine, or taking the oil out of the fuel in a two stroke.
