Had the local mechanic replace my thermostat, as well as do a flush (with flush treatment) and refill. The owners manual says 10 quarts (well, 9.9) on the 2.5 4cyl engine for the coolant capacities. I brought him 3 gallons (12 quarts) of the good stuff from the Mazda dealer, but he only used 1.5 gallons (6 quarts).
He swore it got topped off when I asked him about the extra coolant he returned to me. I trust him....a good mechanic and good guy. But I don't know about his flunkies who work for him.
I only live 5 blocks from the shop so no issues on the return trip home.
Is 9.9 correct? Or is he right by using only 6 quarts?
In short, I think I have a whole extra gallon of unused and unopened coolant with me now, plus another half gallon opened.
And it is at the full line and the coolant in the reservoir looks good (as far as i can tell).

 

10 quarts would be a completely dry engine. 6 quarts sound about right for simple drain & refill.