I accidentally discovered my oil leak when I changed out the oil pump.  The old mouse eared gasket again got hot, expanded and buckled inward, so as to then pump oil straight outside of the gasket containing boundary.  For my new mouse eared gasket install, I RTV'd the offending portion of the gasket in place, so that it cannot buckle and leak.  My mysterious engine oil leak then completely disappeared.

I think I have just used a grease to hold things together for assembly. Good work on your part. Problem solved until the next one rolls on ...

Sure, grease will hold it in place for assembly.  But what I was referring to was when the engine oil heats up over and over again, it expands the rubber of the seal and then causes it to buckle inward and break the oil seal, causing oil to leak out onto the oil pan and drip onto the ground at a prolific rate.

That's how you know there's oil in them, right?