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Both the pH and refractometer -- I'm glad I asked, thank you for correcting me.  Interesting how you put it, I never thought of coolant like oil but it makes sense.


I did not know that the newer "lifetime" coolant wasn't really lifetime but since you are comparing it to oil it then goes without saying.  Of course people talk about oil all the time but you don't really ever run across too many conversations about coolant (despite the fact that it's also critically important).


What specific kind of water are you using with the pre mix (anything beside distilled water)?  Also is there a specific brand or type of antifreeze you prefer?  When I just did my overhaul over the summer part of the work involved dumping and putting in new coolant (at least I know lifetime coolant means if you're dumping it to do work put in fresh fluid when you're done) and I just went with the OE coolant which I would have to go back and look but I'm pretty sure came pre-mixed.  To that end I have been overly paranoid about any fluids in my vehicles in general always using OE fluids for everything after the situation with my 996TT Getrag gearbox which was trashed by the previous owner using an aftermarket oil.  Listening to Stan (at GBox) talk about that was something that stuck with me.

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We always used distilled water, which we purchased from a local super market for about a buck a gallon.  Problem with using tap water is the minerals it contains, everything from sodium to calcium (from the hardness), and even some other metal ions, all of which are bad for the coolant long term, and both lead to corrosion and coolant breakdown. Starting with fresh coolant and distilled water, which is what Porsche always recommended, keeps the system clean and the coolant working longer.


There are a lot of really good coolants out there; Porsche's factory stuff is excellent, but even in the aftermarket products like Prestone, Zerex, Peak, and Pentosin are all excellent products, and there are even store brands like NAPA's Long-life all types coolant are also a good choice.  Most are silica free, advanced OAT technology products, which are designed for modern alloy engines.  Sticking with the factory stuff is usually a very safe bet.

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It's interesting that Porsche recommends mixing their OE coolant.  I know they are under the VW umbrella technically now and I just looked and my 2.0T coolant came premixed 50/50.  It's more expensive to buy this OE coolant but, as I mentioned, after being burned for $5K on a gearbox due to someone else's mistake it has made me think twice about trying to cut any corners whatsoever (which is something I never did much of in the first place but I know some people think I'm crazy about OE fluids/parts but once bitten twice shy).


Just curious at what age/mileage did you normally see the coolant start to break down on the aging curve?  I was also wondering what adverse effects acidic pH has on high alloy castings -- does it do other damage aside from breaking down the glycol in the coolant itself?


Thank you for all this information.  I hope other people read this and benefit from it.

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Like oil, how fast a coolant breaks down depends upon several factors, including how and where a car is driven, and the condition of the cooling system (existing corrosion levels, etc.) when the fresh coolant was added, so each vehicle can be different.  Realistically, most coolants tend to be on a downward curve at about 5-6 years, and a candidate for replacement.  But the inherent variability is why you check and test things.


Acids attack metals, and tend to attach softer metals like aluminum faster that hard metals like steel; so the presence of a hot, acidic solution running through an alloy engine is not a good thing.  Most people also forget that the cooling fins in radiators (and oil to water oil coolers) are thin aluminum, which can quickly corrode through and give you leaks.

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On the aging I def agree it's best to test -- I was asking out of selfish curiosity because I dumped my coolant over the summer and it was probably about 6 years old (obviously I will never be able to test it now that it's gone).  I'm not worried or anything.


That's a really good point about the acid and soft/thin metals.  My car has a turbo so the intercooler could corrode as well.


I've been reading your posts for years and still I often learn something new after reading them.  Awesome that you can do all this magic with just a few inexpensive tools.  Thanks again for all the info, I've learned a lot



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My pleasure.  Loren originally set up this site to provide both solid technical information, and perhaps more importantly, a place were knowledge could be shared, in order to help all members learn more about their vehicles and systems, so that they as owners could both take care of them and get the most enjoyment from them. It has always been our pleasure and a privilege to help those who wish to gain and apply that knowledge.  😉

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