I've read a bunch of things on this, who knows what's right.
At 160 degrees supposedly the
oil will eventually turn to sludge.
Oil is supposed to operate at a higher temperature.
At that temperature emissions will be higher. (Not that anyone here cares)
Without a restriction/thermostat your engine will take a long time to warm up, then it may overheat because the water flows too fast through the radiator for it to cool off.
-steve in nj-