Change from Dexcool OAT to HOAT?

Building3

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gelling will not happen unless you deliberately find a very old IAT formula and introduce air into the system.

original green is a garbage low silicate IAT, do not use it in anything. if you’re afraid of a modern coolant attacking solder, use G05, which happens to reboxed in europe as Glysantin Classic antifreeze.
Air will get into the system every time I check the coolant level. I check all the fluids each time I drive the car so I have to take off the radiator cap to check the level. That air would get into the radiator I assume. There's no other way since there is no overflow bottle and the system is not sealed. No, I don't have a stash of old IAT coolant. I would just go on-line to Amazon to make my purchase. Sealed vs. non-sealed system seems to make a difference with Dexcool. The 1966 Mustang just has a cap and an overflow tube to the ground.
 

LDM

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Air will get into the system every time I check the coolant level. I check all the fluids each time I drive the car so I have to take off the radiator cap to check the level. That air would get into the radiator I assume. There's no other way since there is no overflow bottle and the system is not sealed. No, I don't have a stash of old IAT coolant. I would just go on-line to Amazon to make my purchase. Sealed vs. non-sealed system seems to make a difference with Dexcool. The 1966 Mustang just has a cap and an overflow tube to the ground.
Sealed vs non sealed systems make no difference with Dexcool either. Had a 1995 Tahoe with an open system and Dexcool, never once had any issues with it in the 235K miles that it had on it when I sent it to the scrapyard. The misinformation in this thread is amazing like usual. The issue in with the GM vehicles between 96-02 and Dexcool was a gasket issue, period.
 
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Sealed vs non sealed systems make no difference with Dexcool either. Had a 1995 Tahoe with an open system and Dexcool, never once had any issues with it in the 235K miles that it had on it when I sent it to the scrapyard. The misinformation in this thread is amazing like usual. The issue in with the GM vehicles between 96-02 and Dexcool was a gasket issue, period.
I believe you are correct Sir! This is a very confusing subject as I have been following this thread. I have a 2001 Buick LeSabre that runs DexCool. I'm changing the gaskets out because I feel they "are" the real culprit here, not the coolant. I have been debating and reading about switching coolants but so far, I have not read a scientific credible examination of why Dexcool is looked at so negatively.
 
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Here's an excerpt from an SAE article that details the steps Ford took before switching their vehicles to a Dexcool formulation. Unfortunately you can't link to the original article anymore.

Originally Posted By: SAE 8242
Unlike silicates and phosphates, which deplete as they go to work coating the cooling system, OAT-alone formulas have very long service life. But OATs work very slowly, perhaps taking over 5000 miles to form a protective oxide surface. So they are unable to provide the fast re-protection of cavitation-pockmarked surfaces in water pumps. If a cooling system is prone to cavitation and the vehicle is used in the kind of load service that is conducive to it, the pockmarking increases and can corrode, affecting water pump service life. As a result, Ford has continued with the yellow S-HOAT on the older 4.6-L and 5.4-L V8s and will not change, as these engines are planned for phase-out. One of the organic acids, 2-EHA, is a plasticizer, softening some synthetic rubbers and plastics, particularly silicone gaskets and the Nylon 66 used for gasket carriers and radiator tanks. This was another reason for the continued use of the S-HOAT in the 4.6-L and 5.4-L V8s. All OAT-equipped engines have silicone-free gaskets and validated Nylon 66 radiator tanks. Systems with OAT antifreeze are more sensitive to low coolant levels, because the OAT provides best protection when in full contact with coolant passages. The issue is acute with cast-iron engine architectures, but one also exists with aluminum. For the OAT systems, the sensors combine with improved powertrain computer algorithms for detecting overheating and deploying the limited engine performance strategy Ford has been using to prevent damage to engines if coolant level drops significantly. Additionally, Ford upgraded cooling system seals, gaskets, and clamps, and it evaluated (reworking where necessary) the assembly line processes to ensure a full fill. Further, the antifreeze is mixed 50-50 with de-ionized water for consistent new vehicle protection across all product lines.

Ed
 

LDM

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I believe you are correct Sir! This is a very confusing subject as I have been following this thread. I have a 2001 Buick LeSabre that runs DexCool. I'm changing the gaskets out because I feel they "are" the real culprit here, not the coolant. I have been debating and reading about switching coolants but so far, I have not read a scientific credible examination of why Dexcool is looked at so negatively.
The reason why Dexcool has the "reputation" that it has among people who don't know anything about the real cause is the fact that it was the first new long life coolant used by a major car company. The reality was that only the 3.1/3.4, 3.8, and the Vortec SBC 4.3/5.0/5.7 engines had these issues due to the gaskets in the intake manifold not being compatible with Dexcool's new chemistry and they would slowly break down over time. All the other engines that GM used did not have these issues and you never heard about these intake manifold gasket issues. GM still uses to this day Dexcool and none of the vehicles have these issues currently. If the issue was Dexcool, they would have stopped using in 03 and switched to something else. Instead they changed the gasket materials for the effected engines and the problems stopped.

GM is also hardly the only company that has used Dexcool over the years. If it was, there would have been a similar series of issues. But by the time most other companies switched, the issue with gasket material was known and changes were made before its introduction. Same thing goes on just about any old engine that has been rebuilt and Dexcool used in.

Now that doesn't fix the problem of people either neglecting to change their coolant or mixing in the wrong coolants. But that's a user error and has nothing to do with the gasket issue. There were plenty of people back in the late 90s/early 2000s that didn't bother to read that Dexcool label and use the correct coolant, resulting in a sludge mess in the coolant system. Or the people who went 10+ years and never changed the coolant. But that's user error, just like not changing your oil for 30K miles and wondering why your engine is full of sludge.
 
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I am still using DexCool in my 1999 Alero with no issues. Possibly still has some of the original coolant too since I only ever topped off after replacing the LIM gasket and water pump (on separate occasions) and some leaks.
 
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The reason why Dexcool has the "reputation" that it has among people who don't know anything about the real cause is the fact that it was the first new long life coolant used by a major car company. The reality was that only the 3.1/3.4, 3.8, and the Vortec SBC 4.3/5.0/5.7 engines had these issues due to the gaskets in the intake manifold not being compatible with Dexcool's new chemistry and they would slowly break down over time. All the other engines that GM used did not have these issues and you never heard about these intake manifold gasket issues. GM still uses to this day Dexcool and none of the vehicles have these issues currently. If the issue was Dexcool, they would have stopped using in 03 and switched to something else. Instead they changed the gasket materials for the effected engines and the problems stopped.

GM made the switch to Dex-cool right around the same time they switched to a new generation of plastic intake manifolds on the 3800, and 3.1/3.4 V6's. The new gaskets came out actually before Dex-cool was rolled out so some of the affected cars left the factory with the old green coolant and still experienced the same issues. Once GM looked into the issue and resigned the gasket the issues went away. The SBC 4.3/5.0/5.7 gasket issue was never on the same level as the problems with the 3800's and it's a combination of a poor gasket design, weak gasket material and an unforgiving gasket setup on the SBC engines. I'd say most of the SBC intake manifold gasket failures can now be contributed to old age and wear and tear as most of those engines are now 20-30 years old. All of the gaskets on old school engines like the SBC are inferior to modern engines from the leaky cork valve covers and oil pans, the composite head gaskets, to the multi-piece gaskets for wet type intake manifolds. Modern engines use dry type intake manifolds so even if Dex-cool was eating your gaskets (which it isn't of course) there is no gasket in the intake manifold that it is in contact with.
 

Building3

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Thanks again for all of your knowledge about these coolants. After reading your inputs, I guess where I come out is this: Dexcool OAT may need a closed system to work properly, or it may not. The "66 Mustang is an open system so why take a chance? The Dexcool has reacted with some types of plastic parts and some types of gasket materials. I don't know the safe kind from the unsafe, and I certainly don't know what type are in my car, so why take a chance with Dexcool? Even if I decide on Dexcool, Dexcool takes thousands of miles to be effective, but that will take years to happen so I would have an unprotected cooling system. So now it's down to the HOAT or green IAT which now comes in a 5 year variety. HOAT is probably a safer bet in case I don't get all of the Dexcool out of the system. Probably any store brand HOAT will be fine like Prestone, Zerex, Peak for instance. I don't see on the forum that one is better than the others.
 
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Thanks again for all of your knowledge about these coolants. After reading your inputs, I guess where I come out is this: Dexcool OAT may need a closed system to work properly, or it may not. The "66 Mustang is an open system so why take a chance? The Dexcool has reacted with some types of plastic parts and some types of gasket materials. I don't know the safe kind from the unsafe, and I certainly don't know what type are in my car, so why take a chance with Dexcool? Even if I decide on Dexcool, Dexcool takes thousands of miles to be effective, but that will take years to happen so I would have an unprotected cooling system. So now it's down to the HOAT or green IAT which now comes in a 5 year variety. HOAT is probably a safer bet in case I don't get all of the Dexcool out of the system. Probably any store brand HOAT will be fine like Prestone, Zerex, Peak for instance. I don't see on the forum that one is better than the others.
if you want to transition your system to use more inorganic additives, BMW Blue/G48 is your ticket. fairly high silicate count with borates and azoles, while retaining 2eha as the organic additive. G48 proved to be unproblematic in all of its applications and has a track record of full compatibility with both dexcool and european OAT coolants.

G05 is also an option that relies on primitive sodium benzoate, but has molybdate to protect solder and nitrite to further protect iron if that’s of any importance to you. FCA’s blend of non-2eha OAT coolant proved to be extremely problematic when mixed with G05. G48 however can be readily mixed with G05
 
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Building3

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if you want to transition your system to use more inorganic additives, BMW Blue/G48 is your ticket. fairly high silicate count with borates and azoles, while retaining 2eha as the organic additive. G48 proved to be unproblematic in all of its applications and has a track record of full compatibility with both dexcool and european OAT coolants.

G05 is also an option that relies on primitive sodium benzoate, but has molybdate to protect solder and nitrite to further protect iron if that’s of any importance to you. FCA’s blend of non-2eha OAT coolant proved to be extremely problematic when mixed with G05. G48 however can be readily mixed with G05
Thanks for your specific recommendations. Would any G48 or G05 be acceptable or is there something special about the BMW formulation? I am just thinking about ease of purchase. There are more AutoZones here than BMW dealers, but there is always Amazon.
 
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Stick with the BASF blend of G48, avoid Peak OET as they can’t stick to the formula.

You can find it as Zerex G48, BMW blue coolant, MB anticorrosion/antifreeze 325.0 and volvo blue antifreeze
 

Building3

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Stick with the BASF blend of G48, avoid Peak OET as they can’t stick to the formula.

You can find it as Zerex G48, BMW blue coolant, MB anticorrosion/antifreeze 325.0 and volvo blue antifreeze
Great. That's exactly the information I need. I'll do my best to flush out the OAT this spring and transition to the blue G48. Then do the same in the fall to make sure all of the OAT is gone. Zerex is easy. Thanks!
 
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