Good point, Jerry. He could isolate the filter and spin the oil pump also. That would eliminate the act of running the engine without oil being pumped enough to register at the oil gauge.
There is supposed to be a one-way valve in the oil filter...we always called it the leakdown valve and I've also heard it called other things. Normally I don't think about it. As you know it is supposed to hold the oil that is in the filter when the engine is off so the engine doesn't have to re-fill it each startup. With the by-pass filter if it isn't there or isn't working all the oil will slowly drain down and dribble into the oil pan when the engine isn't running. Given the restriction in the oil fill line of the filter, it would take a few seconds before the filter canister filled.
