Or are there some kinds that can’t be mixed with others?
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.
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.
That’s interesting, because according to the MSDS 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.
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.
It’s the 7-10% additives that are incompatible and screw things up.
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.
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.
-
Conventional/traditional
-
OAT organic additive (acid) technology
-
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.*
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:
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.
Motorcycles have specific requirements: antifreeze must not have silicates. (Not sure what “silicates” are doing in antifreeze.)
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.
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.
I suppose it’s possible some of the inhibitors or dyes react. I’m skeptical though.
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.
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.