With no filtration, a model A engine is a short time schedule oil change interval engine. This would be 500 miles or 6-months whichever comes first. Using full synthetic is kind of a waste of money since it has to be changed so often.
A fully filtered oil system requires all pressured oil to be filtered prior to delivery to the bearings. A Burtz engine will likely do that, other wise a stock engine will have to be modified to do that. Ford used partial filtration for years which increased the oil change intervals but not by a lot.
Modern cars can go a lot longer due to fuel injection and much better efficiency. The problem now is that the over regulation of economy levels has forced the manufacturers to engeneer them to use such thin viscosity lubricants that they no longer get adequate bearing lubrication. This is why so many new engines are failing well before their specified life interval. The bearings need more clearance to run the higher viscosity but that decreases fuel economy. There is always a tipping point to engine design when too much is expected of it.
Like it or not, a lot of used engine oil is being recycled. Recylers don't care if it's mineral based oil or synthetic. It all goes in the same vats for running through the process of filtering out the contaminants and running it back through refining processes. There is no way to separate synthetic from mineral unless re-fractionation can separate them. I'm not sure how that goes in the end product. Ester based synthetics tend to vaporize under high temperatures where mineral based will catch fire at lower heat ranges than synthetics. This is why they are used in turbo shaft and jet engines exclusively. Air cooled reciprocating engines in aircraft had too many failures with full synthetic lubes so they made the manufacturers blend it or use mineral base oils. Liquid cooled engines can take the full synthetics but I still don't use them in any of my vehicles.