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Overview

Auto coolants used to be simple. Every two years you flushed your out your old coolant and replaced it with new you got from your auto supply store.
Recently (1994-96 for GM, 1997-98 for VW, 2002-03 for Ford, 2001 for Chrysler, ...) manufacturers started using extend life coolants with different anti-corrosives for longer life (because people neglected to change it every two years). Some were hybrids with combinations of the new organic acid technology (OAT) and old ingredients like phosphates. The europeans (VW, BMW) didn't like phosphates because of the reaction of their hard water with phosphates; The Japanese (Honda, Toyota) on the other hand liked phosphates because they worked better than borates. So manufacturers started selling proprietary formulas in a variety of colors other than the traditional green and specifying that you use their brand, which was, of course, more expensive.

Many of the owner's manuals will say something like Subaru's:

"The SUBARU Genuine Coolant containing antifreeze and anti-rust agents is especially made for SUBARU engine, which has an aluminum crankcase. Always use SUBARU Genuine Coolant, since other coolant may cause corrosion."

Most experts agree you don't have to use the manufacturers coolant. The new extended life coolants from Zerex, Prestone, ... will be just as good.

The new antifreezes or Extended Life Antifreeze Coolant (XLC or ELC) use Organic Acid Technology (OAT) containing neutralized organic acids (organic acid salts) that protect engine parts from corrosion instead of the inorganic inhibitors such as silicates, phosphates and / or borates in the old (green and yellow) antifreezes.

OAT is recommended in engines with aluminum components (heads or radiators) such as Subarus and VWs because Borates can be bad for them. OAT coolants also have extended lives, up to 150,000 mi.

Hybrid OAT (HOAT) coolants, such as "Zerex G-05." Use organic acids, but not 2-EHA (2-ethylhexanoic acid) (different organic acids are used). Hybrid OAT coolants add some silicate to provide quick-acting protection for aluminum surfaces.


Properties of Organic Acid Technology (OAT) Coolant:
 * Lower alkalinity
 * Contains NO silicates, resulting in longer lasting water pump and engine seals;
    longer shelf life.
 * It is Nitrite-, borate-, phosphate-, nitrate- and amine-free.
 * 100% biodegradable in its pure unused condition.
 * Longer lasting 
Several web sites said you should avoid mixing traditional coolants (blue, yellow or green) with Organic Acid Technology (OAT) (orange, red, pink) or HOAT (yellow) coolants. The OAT will cause precipitation of silicates in the green type and corrosion protection is greatly reduced.

However, many of the aftermarket coolants (e.g. Prestone, Zerex, Peak) now have a universal coolant they claim is OK to mix with anything.

According to Car Talk SAE (the Society of Automotive Engineers) said that you can mix up to about 15 percent traditional coolant in your OAT coolant before you have any real effect on the corrosion inhibitors.

Details

Following are statements from a variety of web sights such as Car Talk, Jiffy Lube, the back of anti-freeze containers, and other sources. Some may be several years old, so don't take into consideration the new "universal" formulas.

As of 2006 I found a lot of conflicting advice on the Internet and in talking to dealers and repair shops.

There were claims that topping off your coolant with the wrong kind or replacing your coolant with a different kind without completely flushing your system could damage your engine and void your warranty.

Many of the aftermarket coolants (e.g. Prestone, Zerex, Peak) now have a universal coolant they claim is OK to mix with anything. Jiffy Lube carries 3 types: 1. Conventional, 2. Dex-Cool (GM) and 3. Prestone OAT for Ford & Chrysler. If you have a VW or Audi you must bring your own coolant and they will use it with their flushing machine.

The bottom line is to check your owners manual (or a label next to your radiator fill cap or overflow reservoir); If it says you must use a special (long life or other designation), don't use the old anti-freeze you've had sitting in your garage for the last 8 years.
However, most of the experts think you can use the new

Coolants have several functions: Anti-freeze, anti-corrosive, water pump lubricant & anti-foaming:

Anti-freeze - Almost all use ethylene glycol (EG) or propylene glycol (PG) (newer) for the antifreeze base.
Anti-corrosion -

  • Conventional - Green/Yellow antifreeze contains silicates, phosphates and / or borates as corrosion inhibitors to keep the solution alkaline. This is called Inorganic Additive Technology (IAT)
    European car makers like VW specify coolant additives lacking in phosphates and including borates and low silicates (such as VW's G11 (blue)) because their water is harder and it reacts with phosphates to create aluminum phosphate or calcium and magnesium deposits.
    See more on problems with phosphates at autorepair.about.com
    The Japanese disagree and specify mixtures high in phosphates and low in borates and silicates because they fear lack of maintenance will cause borate corrosion.
    Tap water in North America also contains calcium, but isn't as hard as European tap water so phosphates are considered okay to use here.
  • Organic Acid Technology (OAT) or Extended Life Antifreeze Coolant (XLC or ELC) antifreeze contains neutralized organic acids (organic acid salts) that protect engine parts from corrosion. These include Havoline® XLC, GM's Dex-Cool® (also manufactured by Texaco) and VW's G12.
    Honda has an extended-life OAT coolant that is dyed dark green and does not contain 2-EHA.

    OAT includes such ingredients as sebacate (Toyota & Honda), 2-ethylhexanoic acid (2-EHA) and other organic acids, but no silicates or phosphates (except in the case of Toyota's pink extended-life coolant, which adds a dose of phosphate to its extended-life OAT-based antifreeze).
    Organic inhibitors do not deplete as quickly as the inorganic inhibitors used in conventional coolants.

    OAT is recommended in engines with aluminum components (heads or radiators) because Borates can be bad for them.
    OAT coolants also have extended lives, up to 150,000 mi.

    OAT corrosion inhibitors provide excellent long-term protection for aluminum and cast iron, but may not be the best choice for older cooling systems that have copper/brass radiators and heater cores, especially the lead solder used in them. It depends on the formula.

  • Hybrid OAT (HOAT) coolants, such as "Zerex G-05®" Use organic acids, but not 2-EHA (2-ethylhexanoic acid) (different organic acids are used). Hybrid OAT coolants add some silicate to provide quick-acting protection for aluminum surfaces. Silicate also helps repair surface erosion caused by cavitation in the water pump. Hybrid OAT coolants are currently used by many European vehicle manufacturers (BMW, Mercedes & Volvo) as well as Ford and Chrysler.
    Toyota adds some phosphate to their hybrid.
  • The new universal coolants use unique OAT-based corrosion packages with proprietary organic acids (such as carboxylate) to provide broad spectrum protection.
Colors (Dyes to distinguish types):
Note: GM converted to OAT (Organic Acid Technology) in 1994-96, but some manufacturers and models were still using conventional coolants in 2005, so check your owners manual to see what you should be using.
Color Mfg Conven-
tional
Conven-
tional
w/ SCA
w/o Phos-
phate
Hybrid
HOAT
OAT
2-EHA
OAT
other
Green Texaco and Shell X        
Yellow Prestone X        
Dark Green Honda ‡         X
Blue VW G11   X      
pink/
red
VW G12         X
Orange GM
Prestone†
Dex-Cool
      X  
Red/
pink
Toyota1     X    
Yellow * Mercedes
G-05
    X    
Red * chrysler ≥2001     X    
Yellow * Ford G-05 ≥2002     X    
Blue BMW    X    
Yellow Zerex G-05     X    
Amber PEAK
LongLife
        X
Brown Brown could mean several types have been mixed, Or reddish-brown rust if the coolant hasn't been replaced for a long time.
In either case you should flush your cooling system and add new coolant.
Truck/Diesel Coolants
Red Zerex, shell ...
Truck ELC
      X
pink Fleetgard
Fleetcool
  X X   X
Source: Universal Coolants at aa1car.com, Coolant Color and its Significance, 2003, at valvoline and various others.
* I have seen web sites which claim Ford uses orange & Chrysler uses Yellow colored coolant and vice versa. I went to Ford and Chrysler dealers and looked at what was in the radiator of their 2006 cars and asked what the parts departments sold which is reflected above.
In Apr. 2006 the Prestone in my auto supply store had "Dex-Cool" on the label, but their web site just listed an extended Life Antifreeze/Coolant which is compatible with ANY antifreeze/ coolant - regardless of color.
Honda - There are pages on the Internet which claim Honda has a Dark Green OAT coolant. I talked to my local honda parts dept. and Jiffy Lube and they both said all Hondas still use conventional coolant.
1. Toyota -
TSB - PG010-02 in 2002 says "The new pink coolant is 100% compatible with the current red coolant and red coolant can be used to replace, top off, or mix in with the pink coolant with no adverse effects."

A Subaru bulletin says:
"Be certain not to substitute the long-life OAT type found in certain domestic cars. Use only a phosphate (non-amine) formula.Read the label carefully to be sure. "
See more Subaru notes below.

One forum said Peak Global LifeTime is OK for Subaru another said it contains silicates which can degrade an aluminum radiator.

SCAs - supplemental coolant additives
2-EHA - 2-ethylhexanoic acid
OAT- Organic Acid Technology
HOAT - Hybrid OAT
XLC or ELC - Extended Life Coolant
LLC - Long Life Coolant
TSB - Technical Service Bulletin

Quote: Tom Magliozzi of "Click and Clack the Tappet Brothers" on Car Talk said: "We knew the color thing had gone too far when we went to Kmart and saw a whole new line of Martha Stewart Coolants."
...
"And by the way, as long as you're using the correct type (traditional or long-life), you don't have to buy the expensive Toyota stuff -- unless, of course, it matches one of the color schemes you've got going under your hood there."

Heavy duty antifreezes require supplemental coolant additives (SCAs) to provide cavitation protection. Cavitation is cavities or bubbles formed at the water pump causing turbulence, loss of pressure and damage to the cooling system.
See: Bubble Trouble, Motor Age, Apr. 2004

I went to Jiffy Lube to see what they used. It is as follows:

  • Ford, Chrysler - Havoline long life for Ford and Chrysler
  • GM - Penzoil Dex-Cool
  • VW, Audi - None - You have to bring your own.

Products:
Prestone makes a GM equivalent with the Dex-Cool label which they claim is also compatible with Ford specs and is good for European and Japanese cars also.

PEAK makes a Extended Life CF-EXL that meets Ford specs as well as two universal coolants (PEAK® Long Life & Peak Global LifeTime). They advertises it can be used when topping off any color antifreeze, but to get the long life you need to flush your cooling system to get rid of all old coolant.
Valvoline's Zerex brand offers several types of automotive antifreeze. They include a conventional green coolant; Zerex ExtremeLife, a Dex-Cool- approved coolant; and Zerex G-05 -- approved for the Ford/Chrysler hybrid specifications.

Truck Extend Life Coolants (ELCs) for diesel truck engines are offered by Cheveron/Texaco, Xerex and Shell. They are usually red.

Fleetgard offers a "Fleetcool" for trucks which is pink.

The "DexCool" designation means the coolant passes General Motors performance testing. Although DexCool is not a specific formula, all three brands that have the label (Texaco Havoline, Prestone Extended Life and Zerex Extended Life) are somewhat similar. In particular, they're OAT coolants, but the similarities go beyond that basic description. All DexCool-approved coolants to date use two organic acid rust/corrosion inhibitors, one called sebacate, the other called 2-EHA (which stands for 2-ethylhexanoic acid).
The term "orange coolant" has come to mean a DexCool-approved.

Toyota and Honda have indicated they absolutely, positively don't want DexCool-type coolants used in their vehicles.

Life:
OAT & HOAT: Five years or 100,000/150,000 miles in newer vehicles (1996 and later).
Useful life is about four years or 60,000 miles in older cars.
Green/IAT: Two to three years and up to 30,000 miles.
The freeze protection level of a coolant mix has little relevance to the corrosion protection afforded by the coolant mix.

General Guidelines:

  • Don't mix traditional coolants (blue, yellow or green) with Organic Acid Technology (OAT) (orange, red, pink) or HOAT (yellow) coolants. The OAT will cause precipitation of silicates in the green type and corrosion protection is greatly reduced.
    Most experts say it is OK to replace non-2-EHA OAT coolants (e.g. VW G12) with 2-EHA (e.g. Dex-Cool)
    According to Car Talk SAE (the Society of Automotive Engineers) said that you can mix up to about 15 percent traditional coolant in your OAT coolant before you have any real effect on the corrosion inhibitors.
  • Use at least a 40/60 mix (40% antifreeze/60% water); 50/50 is most common. Antifreeze should never exceed 65%.
  • Use distilled water if you water is at all hard.
  • Never top off coolant tank with straight coolant-preferably small amount of distilled water or your 50/50 mixture.
  • The anti-corrosion properties will usually break down before the antifreeze, so just because anti-freeze test says you are OK doesn't mean you are protected from corrosion.
  • Adding aftermarket wetters and boosters is not smart because you are altering the already unknown alkalinity of your coolant
  • Some OAT coolants are advertised as "lifetime" but most mechanics recommend replacing them every 3-5 years.
Aluminum is especially vulnerable to corrosion and many vehicles have heads, radiators and other aluminum components in the cooling system.

There is currently a debate as to whether or not Dex-Cool protects lead solder in copper/brass radiators and heater cores. If you have to change a radiator or heater core, use aluminum.

Green antifreeze contains silicates, phosphates and / or borates as corrosion inhibitors to keep the solution alkaline. As long as the solution remains alkaline, corrosion is controlled and the system is protected.

Properties of Organic Acid Technology (OAT) Coolant:
 * Lower alkalinity
 * Contains NO silicates, resulting in longer lasting water pump and engine seals;
    longer shelf life.
 * It is Nitrite-, borate-, phosphate-, nitrate- and amine-free.
 * 100% biodegradable in its pure unused condition.
 * Longer lasting (Dex-Cool has been shown to remain above 95% of its
                original concentration after 150,000 miles in automobiles)

For future servicing convenience, it may be desirable to update the specified coolant in an earlier vehicle by replacing it with Unipart OAT (XLC). This is permissible, provided that the cooling system is first drained and flushed at low pressure. When Unipart OAT (XLC) coolant has been added to such a vehicle, it will be necessary to replace the existing black filler neck label with the OAT warning label (part No: PAK100410A), to indicate the coolant specification has been changed.

Federal Law, the Magnuson-Moss Warranty Act, 1975, prohibits a manufacturer or dealer from voiding your warranty just because you have chosen to use an aftermarket antifreeze/coolant in your automobile.
Requiring a consumer to buy a product from a particular company for use in your automobile in order to be eligible to receive protection under your owner's warranty is an example of a "tie-in" provision. "Tie-in" sales provisions are generally prohibited under the Magnuson-Moss Warranty Act. If federal warranty protection is denied, contact the FTC at (202) 326-3128 or www.ftc.gov.


Flushing
Remove the radiator cap and open the drain cock with a cool engine.
Make sure you drain your overflow reservoir and turn on your heater to drain the heater coils also.

Some sites say "Do not run the vehicle while flushing the system. Even though this would likely do a better job, the cold tap water running from your home may cause aluminum engine components to warp as the engine heats up."
The instructions on the back of the chrysler coolant says to flush for 10 minutes with the engine running.

Refilling:
Check for air bleeds on the engine. Sometimes you'll see an obvious air bleed, such as a boltlike item threaded into a hose. If there's an air bleed, open it. If there are several, open them all.
Some engines also have an additional plug on the engine block which can be removed for more complete draining.

After the first drain, fill the system as well as you can with water, then warm up the engine and let it cool. Drain the radiator again and fill it once more with water. Repeat.

VW recommends a low pressure water and compressed air flush because up to a third of the coolant is still trapped in the heater core and the engine after you pull a hose or the drain cock.

Many shops and quick-change oil centers have special flushing machines which use air pressure or vacuum to get a more complete flush.

Dispose the old coolant properly (see some of the links below). Ethylene glycol, while toxic at high concentration, is highly treatable at the concentrations received by a wastewater treatment plant. If your car has a copper radiator or heater core, the coolant is contaminated with lead solder.

See:
How to flush your radiator / cooling system at TechGuys.ca
Coolant Confusion page 4 for some examples of coolant exchange machines.
How To Flush A Cooling System, 2002, at CarCentral.net
Flushing Your Cooling System, 1997, at Popular Mechanics


VW - Volkswagen

According to one report VW switched from G11 (blue), a phosphate free coolant, to G12 (red/pink) Organic Acid Technology (OAT) Coolant in mid-year 1997 for engines with their new metal head gaskets. Apparently G11 didn't agree with them.
Chris Lagattuta says "I really doubt that the new metal gasket is the reason for the G12. There is actually no bare metal on the gasket and all the passages have sealer from the factory around them. I think the reason was simply that G11 didn't provide long enough reserve capacity and coupled with poor maintenance, they were getting too many warranty problems.

Late (at least 1998 +) model VWs require antifreeze with non-phosphate corrosion inhibitors which meet specifications BS6580 and BS5117 suitable for use in mixed metal engines.

An article at the MG Fan club site in Germany states: "Ob Du G11 (blaue od. grüne Farbe, silikathaltig) oder G12 (rote Brühe, silikatfrei) brauchst kommt darauf an, was drin ist..
G11 und G12 nicht mischen, sonst kann die Kühlflüssigkeit aufschäumen und die Kühlung des Motors ist gefährdet.

Wobei G11 ist bei VW durch G12 Plus ersetzt worden."

My translator came up with the following translation for the above:
"Whether you need G11 (blue od. becomes green to color, with silicates) or G12 (red bruehe, silicate-free) arrive on which in it is. G11 and G12 do not mix, otherwise the coolant can up-foam and the cooling of the engine is endangered.
Whereby G11 was replaced with VOLKSWAGEN by G12 plus."

VW G-12 (Red) antifreeze is not the same as DEXCool Many people recommend against changing from G11 to G12.

He claims first-hand experience in G12 eating the head gasket of a car that was switched from the factory fill of G11. He said that the cooling system was evacuated, and flushed with water before the change. The G11 is soaked into the gaskets, and can't be flushed out of them quickly. When the G12 meets the G11-soaked gaskets, he says they turn to mush in a few weeks.

Advantages of G12

  • Improved corrosion protection
  • Improve thermal stability
  • Improved heat transfer/control
  • Improved hard water tolerance
  • Improved environmental protection
The G12 bottle says your mixture should not be less than 40% G12 (and 60% water).

Sorry to tell you that any other coolant mixed with VW G12 can lead to some real problems like gelling . Another brand that is compatible is Pentosin . Take a look at the color of the coolant in your cars reservoir and see if it has turned brown instead of the light red it should be . If so get it flushed soon .

cartalk.com/board/showflat.php?Cat=0&Number=261605&an=0&page=18 Yes, you do need to use "G12" fluid, mixed with the appropriate ratio of DISTILLED water (gets pricey, I know). The most recent VW pubs I've got are a couple of years old, so I think they are up to "G12 A8F" - don't worry, all G12's are mixable. DO NOT use G11 - the two mix to create a lovely "jello" like material - not good inside your system.

I think (not sure - please post if you can correct me) that it's made by "Pentosin" - a German company. Even though it's pinkish/red, it does not mix with "Dexcool" or similar products. Do a google search, and you should find plenty of sources. It's pretty widely available in DC area.

Phosphates that are in most over the counter antifreeze will ruin the seals in the Volkswagen water pump and cause electrolysis in the Volkswagen radiator because it is made of aluminum.


Subaru:
From SubaruTech Tips: Cooling System Conditioner: Since June of 2003, the Cooling System Conditioner (designed for sealing external leaks on phase two 2.5L) has been added in production on all 2.5L Phase II engines (this also includes the 2.5L Phase II turbo engine). In addition to the 2.5L Phase II engine, Fuji Heavy Industries Ltd. and Subaru of America, Inc. have determined that this product is safe for use in all Subaru vehicles. Therefore starting with the introduction of the Phase II 2.5L engine (1999 model year Forester and Impreza), Subaru of America, Inc. has updated all of the Service Manuals to reflect the adding of the conditioner whenever the antifreeze is drained and replaced.

"Do not use a flushing machine to service Subaru cooling systems. If the machine has been used to service other makes of vehicles that may have copper/brass radiators, a chemical reaction between the copper ions and Genuine Subaru Long Life Anti-Freeze Coolant may occur, which could cause clogging of the radiator."

Be VERY CAREFUL what engine coolant you use -- it must be completely safe for ALUMINUM ENGINES specifically. There are a few low-cost brands out there (Peak, for one) that contain silicates which can degrade an aluminum radiator and even cause engine block wear. Both my dealer and their lead shop mechanic said WRX models in particular should use the factory Subaru fluid (which they sell in gallong jugs as well) and nothing else, because of this danger. Normally I would be skeptical, but the mechanic pointed out that they could actually make more money selling a brand-name fluid to customers -- they would just rather take the loss and avoid replacing radiators under warranty.


Other notes from various Internet sites:
Toyota uses a red antifreeze in many of its products and should not be confused with the orange type long life antifreezes. It is essentially the green type of antifreeze that contains red dye to give it the red color.

For optimum year round protection against freezing, boiling and corrosion, a 50 percent Dex-Cool solution (1 part anti-freeze/1 part water) is recommended. For maximum protection against freezing in extremely cold areas a 60 percent solution. (3 parts anti-freeze/2 parts water) can be used. Concentrations greater than 67 percent or less than 50 percent are not recommended.

If green coolants become mixed with Dexcool(R), however, one study showed a possible aluminum corrosion problem in certain situations. I would not recommend using Dexcool® in a vehicle that did not come from the factory with Dexcool®.

Stay away from 'organic based' rust inhibitor additives. They originated in Euro/Asian markets and are not compatible with Dex-Cool.

Cummings diesel engines have silicone seals in the engine and do not recommend use of orange antifreeze because the organic acids will cause degradation of the seals after 80,000 to 100,000 miles of use.

Both ethylene glycol (EG) and propylene glycol (PG) are used as the antifreeze base. Propylene glycol, like alcohol, is not toxic at low levels. In applications where ingestion is a possibility, PG based antifreeze is a prudent choice.

Try going with about 65% water/ 35% coolant. The coolant is there to not freeze and not boil- water is the best heat exchanger. I also recommend using a product like Redline Water Wetter. The car will run cooler with no other mods.

Phosphate inhibitors

  • Protect aluminum engine components by reducing cavitation corrosion during high speed driving.
  • Provide for corrosion protection to ferrous metals.
  • Act as a buffer to keep the antifreeze mixture alkaline. This prevents acid build-up that will damage or destroy metal engine parts.

BORATES are NOT used by Japanese OEMs due to aggression to aluminum engine components.

Concerns with phosphate containing products are the potential for solids dropout when mixed with hard water.

Another problem was clogged radiators from antifreeze mixtures incompatible with aluminum.

prestone just came out with this new "yellow" antifreeze which is supposed to work in any make/model car on the road plus mix with any color antifreeze on the market.

The House Subcommittee on Environment and Hazardous Material is reviewing the bill to add Denatonium benzoate, a bittering agent, to make their otherwise sweet-tasting product less appealing to animals and children.

Standards:
SAE - Society of Automotive Engineers: J-1023 and J-1034
American Society for Testing and Materials - ASTM D-3306, D-4340, D-4985
  Engine Coolants Testing
MS-9769
British Standards - BS6580 and BS5117

Glossary:
ASTM -American Society for Testing and Materials
EG - ethylene glycol
ELC - Extended Life Coolant
HOAT - Hybrid OAT
LLC - Long Life Coolant
M.S.D.S. - material safety data sheets
OAT - Organic Acid Technology
PG - propylene glycol
SCAs - supplemental coolant additives
TSB - Technical Service Bulletin
XLC - Extended Life Coolant
2-EHA - 2-ethylhexanoic acid

OAT is recommended in engines with aluminum components (heads or radiators) such as Subarus and VWs because Borates can be bad for them. OAT coolants also have extended lives, up to 150,000 mi.

Hybrid OAT (HOAT)

See:
About
U. Tenn.
Dex-Cool
Consumer complaints about DexCool in GM Engines
It's a colorful world: antifreeze/coolant continues to evolve - Aug, 2005 Aftermarket Business
Coolant Color and its Significance, 2003 at valvoline.
Coolant Confusion at V6Performance.net/forums
Coolants Matrix at EET industrial waste management.
Choosing The Right Coolant Popular Mechanics 1999
VW Passat coolant at Maximum Autoparts
Universal Coolants
Bleed the Coolant System at the MG Fan club site in Germany

last updated 20 June 2007