I just recalled a shocking moment of realization I had when working on Formula Ford race cars. A number of drivers were complaining of water and
oil temps generally being to high (usually at the end of a race). So I tested 4 or 5 cars with a calibrated thermometer as well as other primitive methods to compare the readings to the GUAGE readings.
What I found was that the first one or two inches of the sensor lead as it left the sensor itself would easily influence the guage reading! In some cases the sensor would pick up heat from the headers. Or be COOLED by air flow. Then there was the simple fact that some of the guages read incorrectly by up to 10 degrees (high or low, 20 degree spread) under 'perfect' conditions.
Bottom line, I insulated the sensor sending wire\tube as it exited the sensor itself for better reliability of a 'true' reading. Something I HAVEN'T done with my ERA, but it's on 'my list' of things to do...
One such 'primitive' test was: Take off the radiator cap, run the engine and wait until the water 'boils'. THAT is 220, read the guage, does IT say 220? Primitive, but I think fairly effective. As to
oil temp, WHERE are you measuring it?
Oil splashing off the head is WAY hotter than the 'average' oil temp within the pan. I'm not sure 'average' oil temps below 220 (guage reading if you believe it) are necessarily a 'bad' thing. Any residual moisture is dissipated when the oil comes into contact with the very hot head and cools as it returns to the pan.
...not a big fan of oil coolers in general, but they look good!