Head temps are a good thing to measure, but attachment at the spark plug in
the VW can give inaccurate/misleading information. Oil temps are much easier
to use and install. Where is yours installed? In the sump plate is a good
compromise between ease of installation and accuracy, in the oil pressure
outlet is not good--you are measuring engine case temps, not oil temp--you
want it where there is some flow. That can affect the reading. Around 180 in
the winter is OK with a functioning thermostat. 220 is as high as I LIKE to
see mine--I'll accept higher for hill-climbing or strong headwinds, but not
for long, and I wouldn't expect 220 in cool weather (temps under 70 are
winter).