I solved my own question and posted it on stack exchange mainly because I couldn't get any real answers here. If you're interested, it's at this link ---> https://mechanics.stackexchange.com/...antly-replaced
@ermax, I think you meant "shouldn't", and I don't know, I just checked and my coolant reservoir is at the low mark. I will more than likely add some in and frequently check for any changes. My question is unspecific to any issue.
@mav1178 I'm not sure what you mean by this ---> "Topping off when needed" is great if it was pure water and nothing else..."
@Capt Spaulding I encourage you to read my post on stackexchange. You may have a different perspective on the issue.

Cool story except you didn't answer your own question.

Really? That's your own answer to your own question?

I think we need to start another thread to discuss this same topic.

My response was meant as a joke. I.E. a car that is in such bad shape that it's hemorrhaging coolant and oil so fast that you are, indeed, constantly replacing it, has problems far beyond what a fluid change can address.

To the extent that your initial question, "What is the point of changing coolant if it's getting constantly replaced?" could be answered it was addressed early in the discussion. 1) It's NOT getting constantly replaced, so 2) Its anti-corrosion properties degrade with time and "use" 3) and the degraded chemical compounds (combined with other foreign matter) precipitate out of the solution and need to be removed from the system and replaced by fresh fluid.

In essence, you could not answer your own question because it contains a faulty assumption - that the coolant is "constantly being replaced."

@mav1178 - Um, but I did. @Capt Spaulding - It doesn't get constantly replaced, we already know that. You don't need to keep beating the semantics of the thread title. I already mentioned replenished in the description.

If the entire cooling system was closed, then "topping off" would never be a phenomenon, but it is because the coolant reservoir vents to outside air, but nobody here has mentioned that, so it IS getting replenished here and there, but rarely necessary. My question was about the dynamics of fluid exchange primarily, no sure why no one could understand that here except for the community on stackexchange.

Well, I don't know about the other FR-Ss but my 2013, with 20 some thousand miles over the past 4 years, hasn't "used" any coolant ....... :popcorn:


humfrz

Well, ghostzfh, I reckon you are either just yanking our chain or you're waaaay overthinking this situation ........ :iono:

Since you're at 10,000 miles, you have several years/miles before the coolant replacement is scheduled.

I suggest you relax and enjoy driving your machine ....... :thumbsup:


humfrz

I understood your question perfectly.

If you think stackexchange can answer all your questions, why start 3 threads on the same topic?

It's very simple, the mechanism that regulates the cooling system is the thermostat and radiator cap.

The thermostat ensures operating temperature is above a minimum so optimum heat is retained for combustion. There's always an ideal operating temperature given differences in thermal properties of different metallic and non-metallic components of an engine.

The radiator cap basically regulates overheating, in a nutshell. Additives may raise the boiling point of the coolant but the amount of heat that the cooling system can carry away is limited by several factors like ambient temperature, surface area (of radiating surface, i.e. radiator), etc. The radiator cap is designed to hold up to a certain amount of pressure (stock caps usually are 1.1kg/cm2 or around 1.078bar), then the spring releases pressure into the overflow tank ("boils over") and this release in pressure will help reduce the heat in the system. When the engine is cooled down, there will be a vacuum in the cooling system, and it pulls coolant back in from the overflow tank.

The overflow tank needs to be refilled when it is excessively low, yes, but I get the feeling your original question was only with regards to topping off the overflow tank. Topping off this vs replacing your coolant at 100k+ miles is not the same thing.

What is the point of all this? Coolant is water + additives. Additives break down over time, the ability of the additives to prevent corrosion inside the cooling system is reduced and thus your ability to cool the engine is compromised with usage/time.

What you CANNOT do is view this fluid exchange as the coolant being "replenished" or "replaced". Nothing about this is changing anything about the coolant in the block, other than replacing what may have boiled over when the car was hot and the radiator cap was venting excess pressure. You should view it as "putting back what was taken out", which means the bulk of the coolant inside the engine is the same.

Or you can spend 30 seconds and Google all this information.

My money is on option #2. You're cooling a lump of metal with an antifreeze mixture and a pump, not building a goddamned time machine. If you drive more than 10 minutes at a time (long enough for the thermostat to open), all the coolant in the system is homogenous...you don't need to worry about what's in the block being different from that in the radiator or the overflow tank. Crrrripes....


Edit...didn't see the reply above, which was a much more thoughtful way to say "stop making something out of nothing"

You know, I've reread the original post and the stackexchange exchange and I'm still not completely sure what the question is. Is it about the thermodynamics of the cooling system and how/why the overflow bottle works as it does? It is still about the "replenishing" of the coolant?

The latter question (which still seems to be at the core of the discussion on stackexchange) is as @humfrz implies (and the folks on SE confirmed) a non issue as there is no meaningful replenishing happening.

edit: If it's just where does the coolant go as the level drops by tiny increments over the years and miles, @steve99 answered that as clearly as can be in another thread.

I know for me, my coolant kept 'disappearing' pretty fast ...
I met a guy that grabbed some electrical tape (I think that's what he used) and wrapped it around the black rubber hose that sticks out of the coolant overflow tank (where you fill it up). After this little bit of 'air-tight' sealing, my coolant has nearly no loss in coolant (just a splash now and then).