To be honest, if you want to accurately and properly sort this (and keep that station), you need to buy a cheap K-type thermocouple temperature meter off Amazon or Ebay.
Establish what knob positions give you what 'unloaded' tip temperatures.
Leaded, on normal, non-problematic boards: 330'C
All else: 350 - 360'C.
https://www.amazon.com/Proster-Thermocouple-Thermometer-Dual-Channel-Thermocouples/dp/B071V7T6TZ
or similar. Otherwise you're just guessing, and you'll trash more value in tips and PCBs than the meter will cost you.
If funds are limited, and you have a half-decent multimeter, you can, in principle just buy a cheap K-type thermocouple probe for $5, and use this chart:
https://www.pyromation.com/Downloads/Data/emfk_c.pdf
to establish temperature from the thermocouple's output voltage without needing anything else.