"They drained the dino oil out of it, refilled with the synthetic and started again. The idle was roughly 500 RPMs faster."
We did several tests like that and the RPM's did increase every time.
My Dad HAD to adjust the valves every so many miles on his 60 bug running Dino oil. Changed to AMZ/OIL went to adjust the valves and they were still right on. Also had to replace the cork gaskets every time but this time they were pliable. He changed to 3x miles and they needed very little adjustment.
My 81 VW PU electric fan never worked. At 150K the cylinder wall taper was 30 thousands and let off one day the the truck kept going. Sucked oil past the rings as they were expanded to their max. Bro in law tore into the engine. The cam looked new with the turning marks still on the cam only part that was shiny was the tip. On the top side of the connecting rod bearing only a small part of the first layer of grey was missing. He was SHOCKED that it had 150K as he said I would have bet money it had only 30K.