OEM Grey 180F & Motorad white 180F are stamped 82C and they should be fully open by 180F.

The generic el cheapo black units stamped at 82C are in fact marked wrong & they are 190F thermostats.

People will argue, but tossing it into a pot of boiling water & using an IR temp gun will confirm the temp pretty close. It’s not going to be NASA accurate but it will give you an idea of the temp.

I got to the bottom of the generic el cheapo 180F saga when I tossed it into a pot of boiling water along with a confirmed OEM 190F thermostat. They ended up opening fully only like 5 seconds apart. I then removed the el cheapo so called 180F and removed the 190F and cooled it down (cold water for 5min). I then placed the confirmed 180F into the pot with the 190F and boiled the water again. The confirmed 180F opened much sooner like it’s supposed to.

 

That's interesting. I thought the stamped temp was when they started to open? I genuinely can't find a temperature stamped on mine, so it's a bit of a moot point, but it's good to know.

I've been testing mine with an electric kettle that has variable temperature control. Maybe I'm just paranoid, but it seems like having a plastic housing resting on the bottom of a pot of boiling water is a recipe for a melted thermostat.

Just to be clear before I invest in another thermostat that's not as advertised, this is the Motorad that you're referring to?

 

Looks like the unit I get locally from Auto Zone yep