Forgot to mention, mid August, about the same time as I did my Tb, I did another partial coolant change. My rez truck has somewhere around 381,000km and the coolant began to freeze this past winter. We had several days where the ambient was around the -40C mark. Noticed coolant had leaked out into the snow and found it partially frozen. I plugged in the block heater and got it running. Well when the thermostat opened there was no room for the coolant to go as the rad was still frozen. She puked out a gallon or more. So I topped it up and ran it for a few more months and then drained the rad again for another partial change.
I used "certified" brand from Cambodian Tire, the generic green stuff. I have close to 3 gallons of fresh coolant in her now.