Temperature fluctuations after t-belt/thermostat replacement

Hello again. Thanks, everyone, for all the advice given in the past several weeks, as I've changed my timing belt and other stuff, and wouldn't have been able to do that without all your collective counsel.

Since replacing my thermostat when I replaced my timing belt, I've noticed weirdness happening:

Old Thermostat was an 82ºC/180ºF model WITH an "air-relief valve" AKA jiggle-valve. Normal operation temp per UltraGauge: 188.6ºF. Rock steady.

New Thermostat: Napa Auto Parts (non factory) WITHOUT an "air-relief valve".

New operation temp: 188º/194º/195.8ºF per Ultragauge. It bounced all over the place from my drive from Seattle to Fairbanks. Settled in on the highest number, 195.8º

Yes, I "burped" it. Squeezed hoses, noticed bubbles, checked the overflow reservoir: every time I think I got more bubbles out, it doesn't make any difference.

I think I changed the viscosity of the anti-freeze too, to make it protect my engine down to -60ºF , and I suspect that change in anti-freeze viscosity might account for something, but I can't seem to get this thing to settle. Should I worry about it? Anyone got any ideas why it won't settle?

 

Sounds like there's still some air in the system, but 195 is nothing.
My '08 runs at 199 or 204.

Could still be the thermostat. I've had more than one off-the-shelf thermostat (and radiator cap) that were not working properly.
Yank that 'stat and put one in from Toyota.
Your factory stat is probably 195 anyways.