# Are all automobile antifreezes compatible? **URL:** \ **Category:** Factual Questions\ **Created:** [January 16, 2008, 6:18pm UTC](https://boards.straightdope.com/t/are-all-automobile-antifreezes-compatible/433759 "2008-01-16T18:18:47Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![Joe\_Mahma](https://avatars.discourse-cdn.com/v4/letter/j/5daacb/32.png) [@Joe\_Mahma](https://boards.straightdope.com/u/Joe_Mahma)\ **Post date:** [January 16, 2008, 6:18pm UTC](https://boards.straightdope.com/t/are-all-automobile-antifreezes-compatible/433759/1 "2008-01-16T18:18:47Z")
Or are there some kinds that can’t be mixed with others? ---
**Author:** ![sciguy](https://avatars.discourse-cdn.com/v4/letter/s/e68b1a/32.png) [@sciguy](https://boards.straightdope.com/u/sciguy)\ **Post date:** [January 16, 2008, 6:27pm UTC](https://boards.straightdope.com/t/are-all-automobile-antifreezes-compatible/433759/2 "2008-01-16T18:27:31Z")
From my experience, there are two “flavors” of antifreeze: green and red. I have been informed that mixing those leads to “bad things” (they use different chemicals to retard freezing, and don’t play well together). But if you’re asking whether Brand X of green antifreeze is compatible with Brand Y of green, then I can’t say for sure. I’d assume so, but not being a mechanic, I wouldn’t take my word for it. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [January 16, 2008, 6:31pm UTC](https://boards.straightdope.com/t/are-all-automobile-antifreezes-compatible/433759/3 "2008-01-16T18:31:49Z")
There’s two primary types - the standard greenish kind that’s used in most vehicles, and an orange/red type called Dex-Cool. I believe only GM uses Dex-Cool. If you car was built with Dex-Cool in the engine, use only Dex-Cool. Do not add regular green antifreeze to Dex-Cool, and if your car uses the normal green stuff, do not add Dex-Cool. Mixing the two types has been known to cause corrosion of engine components, as well as gasket and water pump failures. ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [January 16, 2008, 6:44pm UTC](https://boards.straightdope.com/t/are-all-automobile-antifreezes-compatible/433759/4 "2008-01-16T18:44:47Z")
[QUOTE=gotpasswords] Do not add regular green antifreeze to Dex-Cool, and if your car uses the normal green stuff, do not add Dex-Cool. Mixing the two types has been known to cause corrosion of engine components, as well as gasket and water pump failures. [/QUOTE] That’s interesting, because according to the [MSDS](http://www.google.com/search?hl=en&q=dexcool+msds&btnG=Search) Dex-Cool is 90–97% ethylene glycol. I suspect, GM just wants to make sure you keep buying their coolant, so they tell you how awful combining them is. ---
**Author:** ![Omegaman](https://avatars.discourse-cdn.com/v4/letter/o/e480ec/32.png) [@Omegaman](https://boards.straightdope.com/u/Omegaman)\ **Post date:** [January 16, 2008, 6:50pm UTC](https://boards.straightdope.com/t/are-all-automobile-antifreezes-compatible/433759/5 "2008-01-16T18:50:09Z")
[QUOTE=Christopher] That’s interesting, because according to the [MSDS](http://www.google.com/search?hl=en&q=dexcool+msds&btnG=Search) Dex-Cool is 90–97% ethylene glycol. I suspect, GM just wants to make sure you keep buying their coolant, so they tell you how awful combining them is. [/QUOTE] Not completely true. I work for Chrysler and we have our own brand of long life coolant. Although if you check the military specification for it it will work in place of Dexcool although is a different color. As far as I know regular and long life coolant don’t mix. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [January 16, 2008, 7:11pm UTC](https://boards.straightdope.com/t/are-all-automobile-antifreezes-compatible/433759/6 "2008-01-16T19:11:00Z")
[QUOTE=Christopher] That’s interesting, because according to the [MSDS](http://www.google.com/search?hl=en&q=dexcool+msds&btnG=Search) Dex-Cool is 90–97% ethylene glycol. I suspect, GM just wants to make sure you keep buying their coolant, so they tell you how awful combining them is. [/QUOTE] It’s the 7-10% additives that are incompatible and screw things up. ---
**Author:** ![redtail23](https://avatars.discourse-cdn.com/v4/letter/r/3e96dc/32.png) [@redtail23](https://boards.straightdope.com/u/redtail23)\ **Post date:** [January 16, 2008, 7:21pm UTC](https://boards.straightdope.com/t/are-all-automobile-antifreezes-compatible/433759/7 "2008-01-16T19:21:19Z")
And don’t go just by the color. Somebody\* out there is making antifreeze the wrong color. A car\* needed antifreeze. I looked at the color already in the radiator, and bought that color. Checked the owner’s manual and it was the wrong kind. This was fortunately discovered prior to mixing the two. However, as far as I know, you can mix different brands, as long as they’re the same type. \*I think it was a Toyota, but don’t remember for sure; it wasn’t my car, I was just helping out. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [January 16, 2008, 7:38pm UTC](https://boards.straightdope.com/t/are-all-automobile-antifreezes-compatible/433759/8 "2008-01-16T19:38:34Z")
It is possible to have problems, sometimes significant and expensive problems, as a result of mixing different coolant types, or changing to a different type. Color is not a reliable indicator of the coolant type. The color is from dye, and while each manufacturer may have its own color code, there is not a universally applied standard among different manufacturers. There are three basic types of ethylene glycol antifreeze (see below). The best thing to do is consistently use the type of antifreeze installed at the factory. Below is info from a colleague of mine who is an expert on engine coolants and cooling systems. As you can see, it’s a much more complicated issue than most people realize - and that (sadly) includes a lot of people who make their living servicing automobiles. \*There are three basic types of ethylene glycol coolant. 1. Conventional/traditional 2. OAT organic additive (acid) technology 3. HOAT (Hbrid OAT with silicates) They are all available in every color you can imagine. HOAT are further divided into parially formulated (requires a supplement for diesel applications) and fully formulated can be used as is in diesel applications. The fully formulated can be substituted for partially formulated. The addition of silicates provides fast acting protection that OAT coolants lack and provide a barier that protects plastics from potential deplymerization of some plastics. Fully formulated HOAT Examples: Zerex G-05, Chevron Custom Made, Texaco/Havoline Custom Made, Motorcraft Premium Gold, Mercedes Benz, Freightliner Purple long life, Mopar Long Life Orange, Mopar Long Life Gold/Amber, Peak CF-EXL, MTU Green. Partially Formulated Examples: VW Blue, BMW Blue, Volvo Green, Zerex/Glysantin/BASF G-48 (Saab and others have used this also. If it’s Blue and European OEM, It’s G-48). OAT comes in many varieties. The Japanese have high phosphate versions and a few molybdate versions. Molybdates improve water pump protection. European and American versions are phosphate free. GM and others that are “GM Dexcool approved” and some “one size fits all” versions use a specific 2-EH acid that some OEMs believe cause problems and are dead set against. European and American versions are usually phosphate-free. All are silicate free. Toyota uses a couple of non 2-EH versions with molybdates for extra cavitation protection. Peak Global is a non-2-EH version. Most European red/pink coolants are Zerex/Glysantine/BASF G-30. VW/Audi/porsche, Jaguar and others use it and have used it. GM/AC-Delco/Shell/Chevron/Texaco/Havoline is the 2-EH Dexcool stuff and Zerex/Gysantine G-34/Extreme Life 5/150 is the European Dexcool (Newer Saab etc) with molybdates. Conventional coolants come in passenger car (ASTM D3306) partially formulated HD (accepts supplements for HD service) and fully formulated (Ready for HD service). All include silicates for fast acting protection against abrasives and water pump cavitation. Supplements to address HD cylinder liner cavitation include the SCA/DCA-2 nitrite stuff and the DCA-4 molybdate/nitrite stuff. Silicates can cause problems in some cars Phosphates can cause problems in some cars 2-EH acids can cause problems in some cars Borates can cause problems in some cars Silicates are required in some cars 2-EH acids are required in some cars There is no such thing as a one size fits all coolant.\* ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [January 16, 2008, 7:38pm UTC](https://boards.straightdope.com/t/are-all-automobile-antifreezes-compatible/433759/9 "2008-01-16T19:38:41Z")
[QUOTE=gotpasswords] It’s the 7-10% additives that are incompatible and screw things up. [/QUOTE] I don’t understand how a solution that contains mostly ethylene glycol can be incompatible with ethylene glycol. I can also assure you that potassium carboxylate salts do not react with ethylene glycol in any significant way. from [Wikipedia](http://en.wikipedia.org/wiki/Anti-freeze): > [@](#): > > According to the Dexcool manufacturer, "mixing a ‘green’ coolant with DEX-COOL reduces the batch’s change interval to 2 years or 30,000 miles, but will otherwise cause no damage to the engine. Since this is entirely compatible with my knowledge of chemistry, I accept it as valid. I would need to know the chemistry of other antifreezes to know how compatible they are. ---
**Author:** ![Vorpal\_Blade](https://avatars.discourse-cdn.com/v4/letter/v/9de0a6/32.png) [@Vorpal\_Blade](https://boards.straightdope.com/u/Vorpal_Blade)\ **Post date:** [January 16, 2008, 7:44pm UTC](https://boards.straightdope.com/t/are-all-automobile-antifreezes-compatible/433759/10 "2008-01-16T19:44:05Z")
[QUOTE=Joe Mahma] Or are there some kinds that can’t be mixed with others? [/QUOTE] Motorcycles have specific requirements: antifreeze must not have silicates. (Not sure what “silicates” are doing in antifreeze.) ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [January 16, 2008, 7:58pm UTC](https://boards.straightdope.com/t/are-all-automobile-antifreezes-compatible/433759/11 "2008-01-16T19:58:32Z")
[QUOTE=Christopher] I don’t understand how a solution that contains mostly ethylene glycol can be incompatible with ethylene glycol. I can also assure you that potassium carboxylate salts do not react with ethylene glycol in any significant way. [/QUOTE] It’s not a matter of incompatibility with the ethylene glycol. The concern is how the additives react with the metals in the system and with the different additives of other antifreeze formulations. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [January 16, 2008, 9:25pm UTC](https://boards.straightdope.com/t/are-all-automobile-antifreezes-compatible/433759/12 "2008-01-16T21:25:04Z")
[QUOTE=Christopher] I don’t understand how a solution that contains mostly ethylene glycol can be incompatible with ethylene glycol. I can also assure you that potassium carboxylate salts do not react with ethylene glycol in any significant way. from [Wikipedia](http://en.wikipedia.org/wiki/Anti-freeze): Since this is entirely compatible with my knowledge of chemistry, I accept it as valid. I would need to know the chemistry of other antifreezes to know how compatible they are. [/QUOTE] When I see service bulletins written by the engineering departments of car companies warning against mixing, I tend to believe them. Not just one car company, but several. The engineering department is not in the business of selling parts. They are in the business of keeping the cars on the road. **Gary T** nailed it in post #8 (as usual) ETA: I just called a buddy in tech support for AC/Delco. He is going to send several TSB concerning Dex-cool and standard antifreeze. Stay tuned film at 11. ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [January 16, 2008, 10:52pm UTC](https://boards.straightdope.com/t/are-all-automobile-antifreezes-compatible/433759/13 "2008-01-16T22:52:22Z")
I suppose it’s possible some of the inhibitors or dyes react. I’m skeptical though. ---
**Author:** ![Billdo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/billdo/32/315_2.png) [@Billdo](https://boards.straightdope.com/u/Billdo)\ **Post date:** [January 16, 2008, 10:57pm UTC](https://boards.straightdope.com/t/are-all-automobile-antifreezes-compatible/433759/14 "2008-01-16T22:57:32Z")
[QUOTE=Rick] ETA: I just called a buddy in tech support for AC/Delco. He is going to send several TSB concerning Dex-cool and standard antifreeze. Stay tuned film at 11. [/QUOTE] No, no, no. You gotta do this right: Are _you_ putting _your family’s_ life _at risk_ with your antifreeze? Stay tuned for the news at 11 to see how you can prevent your car from **exploding in a ball of flames.** ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [January 17, 2008, 12:24am UTC](https://boards.straightdope.com/t/are-all-automobile-antifreezes-compatible/433759/15 "2008-01-17T00:24:33Z")
[QUOTE=Christopher] I suppose it’s possible some of the inhibitors or dyes react. I’m skeptical though. [/QUOTE] It’s not the dyes, and it’s not just simple chemical reactions (add A to B and see what happens). Automotive cooling systems proffer a blend of heat, various metals, and flow characteristics that can induce cavitation and corrosion. Cavitation is a potentially major problem, and various additives are used to minimize it. Each additive has its pros and cons, and car manufacturers have different opinions about which ones should and should not be used. There have been cases where using a different (non-recommended) antifreeze has started a chain of events that ends with severe erosion of cylinder heads and engine blocks. It doesn’t happen all the time, and not every mix of different coolants has the same risk potential, but it has happened.