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I know I'm opening up a can of worms, but what's the latest on the coolant we should be using (by the way, I have a 86 944 that had the head eaten by coolant).
I used to use Zerex G-05, have since switched to the Peak Euro, based in part on the thread above (not that they proved anything about Peak, but it did convince me that maybe G-05 was not the best choice). I have not had any issues (that I know of) with either coolant.
I know I'm opening up a can of worms, but what's the latest on the coolant we should be using (by the way, I have a 86 944 that had the head eaten by coolant).
Options:
1. Porsche Coolant (pink stuff)
2. Zerex (G40 - supposedly same as Porsche)
3. Peak European (says <1996 Porsche) - Blue
You have basically two "Porsche approved" choices -
1. The original IAT formulation [in the US it is Prestone Green]
2. Glysantin G-48 Hybrid Organic Acid based coolant known commercially as HOAT.
The G-48 formulation is what VW market as their G-11 coolant, it is coloured blue, it was developed by BASF in Germany under their Glysantin brand name and it is what you get in a jug when sold by Porsche as "their brand" coolant for pre 1996 models - the only difference is pricing. Xerex G-48 is made under license and is the same stuff. Pentafrost NF is also G-48 but for some reason [probably licensing fees] they do not call it such but it is approved by VW as meeting their G11 spec - QED that is also G-48! Other manufacturers also offer G-48 and they are all coloured coded blue such as the Peak coolant you feature. It is called hybrid OAT because the original attempts to make OAT coolant failed to meet expectations back in the early 1990's so BASF took a retrograde step and reintroduced silicates and it worked and in 1994 they introduced their first commercially available long life coolant G-05 as a direct replacement for the previous IAT universal coolant that was a "one size fits all" for over 50 years. I will cover that later on.
The original IAT formulation was superceded for political/environmental reasons [disposal] and as I am concerned remains a superior formulation in terms of corrosion prevention. The political objection to it was longevity in that it was stuffed down users throats that it was only good for two years. Prestone "magically" managed to increase its life expectancy to 5 years or 150k miles just like the 2nd generation coolants. This is what I use and the last batch I changed out after 4 years was in like new condition with a pH of 8.5. [i.e. alkaline]. Coolant life is not determined by mileage or by time it is controled by the number of operating hours at temperature. In our alloy engines the anti corrosion chemicals remain virtually unused because there is virtully no corrosion taking place to consume them but the buffering agent is what gets consumed and why measuring pH of the coolant is indicative of remaining life- I use fish tank test strips to test for pH- simple!
The chemical package in every coolant made today is designed to do a number of things such lubricating the seal of the water pumps and prevent foaming. However the primary tasks are to prevent general weight loss corrosion and [most importantly of all] to buffer the coolant. Most will not understand what the latter item means but in chemistry terms it is most important to keep ethylene glycol alkaline as when exposed to heat above 55C it breaks down to form organic acids such as formic and carbolic acid the consequences of which would be catastrophic for our engines. Although this is technically possible I have yet to see an example of it happening.
With respect to G-05 coolant it was an overnight success when launched in 1994 as there was nothing to compete with it. It has been used in many 928's without problem but there is a caveat. G-05 contains a component known as nitrites. This was added to suit the needs of the US market and is intended to protect diesel engines with wet liners against a phenomena known as cavitation. This is not needed in our motors but does no harm to our engines either. The German manufacturers did not seemingly like this and thus never approved it for use in their motors. The caveat is that some radiator manufacturers use brazing in their alloy radiators to seal the tubes to the tubesheets, some weld them. It turns out that for those brazed, if a certain type of flux is used it can lead to a corrosion attack and leakage. To my knowledge this type of problem does not happen to 928 radiators and hence there is no logical reason to prevent use of G-05 in the 928. That being said given the availability of the formally approved coolants why use anything else these days?
To be clear coolant does not cause corrosion - it prevents such. Ethylene glycol is inert- it is an organic compound [edit]. The potential for corrosion problems lies with the water used in the mix. This is a problem for engines with cast iron blocks and heads [old generation US vee 8's?]. Aluminium alloys form a protective passive coating of aluminium oxide and thus do not corrode unless and until that layer is broken down then all bets are off.
Your 944 cylinder heads did not corrode due to the coolant- they corroded because of what happened to the coolant once it migrated into the gap between the gasket and the head- a problem common to 928's, 944's and 968's. If you have a photo of your head in the corroded condition and the gasket [head side] and post such I will be happy to give you my take on what happened.
With respect to G40 [pink] coolant this is used in modern day Porsches like my Cayenne turbo S. As to whether it would be problemmatical if deployed in our 928's remains to be seen. The VW spec for this stuff is their G-12 and there are three versions of this- the last one of which is allegedly OK for their older vehicles. I did see something that suggested it does not give protection to ferritic steel surfaces but I find that hard to believe. The point is why take a risk if approved coolants are readily available?
Finally the coolant you need to avoid for sure is Dexcool. Mix that stuff with the original IAT coolant and you will end up with a gelatinous goo blocking the entire cooling system. Never mix different classes of coolant- flush with water before doing so.
Last edited by FredR; 11-01-2023 at 04:05 AM.
Reason: added G40 sentence/ corrected error
You have basically two "Porsche approved" choices -
1. The original IAT formulation [in the US it is Prestone Green]
2. Glysantin G-48 Hybrid Organic Acid based coolant known commercially as HOAT.
The G-48 formulation is what VW market as their G-11 coolant, it is coloured blue, it was developed by BASF in Germany under their Glysantin brand name and it is what you get in a jug when sold by Porsche as "their brand" coolant for pre 1996 models - the only difference is pricing. Xerex G-48 is made under license and is the same stuff. Pentafrost NF is also G-48 but for some reason [probably licensing fees] they do not call it such but it is approved by VW as meeting their G11 spec - QED that is also G-48! Other manufacturers also offer G-48 and they are all coloured coded blue such as the Peak coolant you feature. It is called hybrid OAT because the original attempts to make OAT coolant failed to meet expectations back in the early 1990's so BASF took a retrograde step and reintroduced silicates and it worked and in 1994 they introduced their first commercially available long life coolant G-05 as a direct replacement for the previous IAT universal coolant that was a "one size fits all" for over 50 years. I will cover that later on.
The original IAT formulation was superceded for political/environmental reasons [disposal] and as I am concerned remains a superior formulation in terms of corrosion prevention. The political objection to it was longevity in that it was stuffed down users throats that it was only good for two years. Prestone "magically" managed to increase its life expectancy to 5 years or 150k miles just like the 2nd generation coolants. This is what I use and the last batch I changed out after 4 years was in like new condition with a pH of 8.5. [i.e. alkaline]. Coolant life is not determined by mileage or by time it is controled by the number of operating hours at temperature. In our alloy engines the anti corrosion chemicals remain virtually unused because there is virtully no corrosion taking place to consume them but the buffering agent is what gets consumed and why measuring pH of the coolant is indicative of remaining life- I use fish tank test strips to test for pH- simple!
The chemical package in every coolant made today is designed to do a number of things such lubricating the seal of the water pumps and prevent foaming. However the primary tasks are to prevent general weight loss corrosion and [most importantly of all] to buffer the coolant. Most will not understand what the latter item means but in chemistry terms it is most important to keep ethylene glycol alkaline as when exposed to heat above 55C it breaks down to form organic acids such as formic and carbolic acid the consequences of which would be catastrophic for our engines. Although this is technically possible I have yet to see an example of it happening.
With respect to G-05 coolant it was an overnight success when launched in 1994 as there was nothing to compete with it. It has been used in many 928's without problem but there is a caveat. G-05 contains a component known as nitrites. This was added to suit the needs of the US market and is intended to protect diesel engines with wet liners against a phenomena known as cavitation. This is not needed in our motors but does no harm to our engines either. The German manufacturers did not seemingly like this and thus never approved it for use in their motors. The caveat is that some radiator manufacturers use brazing in their alloy radiators to seal the tubes to the tubesheets, some weld them. It turns out that for those brazed, if a certain type of flux is used it can lead to a corrosion attack and leakage. To my knowledge this type of problem does not happen to 928 radiators and hence there is no logical reason to prevent use of G-05 in the 928. That being said given the availability of the formally approved coolants why use anything else these days?
To be clear coolant does not cause corrosion - it prevents such. Ethylene glycol is inert- it is an oil. The potential for corrosion problems lies with the water used in the mix. This is a problem for engines with cast iron blocks and heads [old generation US vee 8's?]. Aluminium alloys form a protective passive coating of aluminium oxide and thus do not corrode unless and until that layer is brken down then all bets are off.
Your 944 cylinder heads did not corrode due to the coolant- they corroded because of what happened to the coolant once it migrated into the gap between the gasket and the head- a problem common to 928's, 944's and 968's. If you have a photo of your head in the corroded condition and the gasket [head side] and post such I will be happy to give you my take on what happened.
With respect to G40 [pink] coolant this is used in modern day Porsches like my Cayenne turbo S. As to whether it would be problemmatical if deployed in our 928's remains to be seen. The VW spec for this stuff is their G-12 and there are three versions of this- the last one of which is allegedly OK for their older vehicles. I did see something that suggested it does not give protection to ferritic steel surfaces but I find that hard to believe. The point is why take a risk if approved coolants are readily available?
Finally the coolant you need to avoid for sure is Dexcool. Mix that stuff with the original IAT coolant and you will end up with a gelatinous goo blocking the entire cooling system. Never mix different classes of coolant- flush with water before doing so.
A bit too much text Fred, but good statements overall. But I cannot ignore things like this statement:
"Ethylene glycol is inert- it is an oil."
It is not, period. It is an Alcohol.
A bit too much text Fred, but good statements overall. But I cannot ignore things like this statement:
"Ethylene glycol is inert- it is an oil."
It is not, period. It is an Alcohol.
Well spotted- a freudian slip [otherwise known as a brain fart] - meant to say it is organic.
In its natural state ethylene glycol is relatively inert and presents no threat to metals but when heated it converts into organic acids and consequently cause aluminium alloys to lose their passivity thus why it is buffered in the original coolant I use by borax. No idea as to how exactly this is achieved in the 2nd generation coolants- presumably pretty much the same.
I have been using the Pentofrost NF now for 4 years after switching from the G-05. IMHO it seems to be the highest rated for our cars other than the Porsche coolant.
10-29-2023, 06:02 PM
What is the latest on coolant choice for 928s?
