Jag_man653.......You got my curiosity going....so I too did a similar experimentation and the max line on the outside is at the proximity to the top of the notch inside. I shined a light inside to the outer reservoir and moved the reservoir back and forth and they are both on the money! I had to take out about 3+ ounces to get it to cover the notch. I'm sure 3 ounces wouldn't make much difference anyway. Thanks for your astute observation.

 

As someone else said, we're both probably "over thinking" this thing.

 

I agree you're overthinking it. It costs roughly $125 to flush the coolant system round these parts plus a small waste disposal fee. I would focus on that vs worrying about topping off to X degree of accuracy. Just sayin. Your bigger issue is whether or not you have to correct coolant. OAT is typically orange and OEM coolant is orange but your's appears all green. OAT does come in green but so do other types. If it were my car, I would get it flushed this week. Cooling systems should be flushed every 5 years anyway and you don't have the history.....