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My car's manual says to use the blue Honda coolant:

Always use Honda All Season Antifreeze/Coolant Type 2 [MSDS]. This coolant is pre-mixed with 50 percent antifreeze and 50 percent water. It does not require any additional mixing. If it is not available, you may use another major-brand non-silicate coolant as a temporary replacement. Make sure it is a high-quality coolant recommended for aluminum engines. However, continued use of any non- Honda coolant can result in corrosion, causing the cooling system to malfunction or fail. Have the cooling system flushed and refilled with Honda antifreeze/ coolant as soon as possible.

On the other hand, Prestone claims their green coolant is harmless:

Prestone® Extended Life Antifreeze/Coolant is compatible with ANY antifreeze/ coolant – regardless of color – for use in ALL makes and models of cars and light duty trucks. This patented formula provides a high degree of performance durability and carefully balanced protection against temperature extremes and rust corrosion of all cooling system metals, including aluminum.

Who should I believe? Will it really result in corrosion if used more than temporarily?

Please provide reliable references for any claim you make. The internet is already full of opinions about this stuff, most of which are contradictory.

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For the most part what the manufacturer is saying...is true. Using an anti-freeze that is not recommended will in fact lead to build up of corrosion in the coolant passages of the engine block or anywhere else it flows. BMW recommends a phosphate free coolant that reduces the chances of corrosion –  Dude318is Jun 14 '11 at 20:43

7 Answers 7

up vote 11 down vote accepted

Every manufacturer recommends their own fluids. Everybody wins because your engine gets "less corrosion" and they great great markup on those things.

A while ago I did cooling system maintenance (replace hoses, water pump, thermostat, temp sensor, radiator cap) on my wife's BMW 330i. That make/model has a lot of following and several high-quality forums with lots of people and lots of opinions. Half the people on those forums are under the impression that if the fluid doesn't have BMW written on the can, it can't touch the car. The other half (equally knowledgeable and competent people) is using Prestone. I have not read any post that suggested Prestone caused any kind of problems.

That's what I've been using in all my cars, including the BMW, and I never had any cooling system problems either. I sold my Integra with 194k and engine was still fine. Rust ate away a lot of the body.

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The formulation of Prestone varies from product to product. In addition, Prestone has changed over the years. It isn't valuable to say that all you've used is Prestone and had not any problems. Cooling systems can have problems with OEM fluid and that wouldn't be an indictment of that fluid. You can have had problems using Prestone as well, but that might have just happened anyway. This is the problem using anecdote to answer broad questions. It requires research and not personal experience. –  geoO Jun 9 '13 at 9:55
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@geoO: anecdote would imply that I simply told you story without any base on facts and moved on. That's not really true. 1) I really do use prestone; 2) I really did go to BMW forums to see what other people say; 3) I really never had any problems with prestone in ANY of my cars; 4) Manufacturers do have other interests in mind when they make their recommendations (my company does same things just with our products, also a fact); 5) I really did observe two groups of people (and like I said both knowledgeable that I would respect)... you clearly being in one of those groups :) –  DXM Jun 9 '13 at 16:47
    
Unfortunately, I've got other things going on in my life that doing full "research" on every product I've ever put into a car would get rather expensive and I'm assuming a lot of other people are in the same boat as me. So I provided an answer based on my experience and my observations of other people's "research", which just happened to be all over the place –  DXM Jun 9 '13 at 16:50
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@geoO: en.wikipedia.org/wiki/Search_cost -- "rational consumer will continue to search ... until the marginal cost of searching exceeds..." -- I have a job. I have a wife. I have hobbies... To me and other people, who found this answer (or forum posts) useful, using "anecdotes" is a way of reducing search costs because to me and many more others, "coolant research" is kinda pushing the limits of what would be considered rational. But clearly, others such as yourself, should simply do the research and use best coolant they can find for their cars. –  DXM Jun 10 '13 at 18:29
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@geoO: ... and I'm not saying you are wrong. In fact I just read your post, +1 to that :) and I will be sure to use my experience of reading your facts in my future decision making process. –  DXM Jun 10 '13 at 18:33

There are silicate antifreezes, used in most domestic cars until recent years, and OAT antifreezes, used in Japanese cars because of their domestic market testing.

Domestic cars today all use OAT now, with Chrysler the last to switch. See

http://www.sae.org/mags/aei/mater/11284

Any OAT antifreeze will work in a Honda, but don't use silicate antifreeze in a Japanese coolant system. Evidence shows it reduces water pump life in certain Japanese import cars.

Prestone Regular or 50/50 is a silicate free OAT antifreeze.

Ultimately it isn't the color but the composition that matters. It was confusing for a while, but since most of the industry went to OAT you can't go far wrong with any name brand off-the-shelf coolant. I don't know about european cars, but the US and Japan are on the same page in 2013.

Also from the link above: "The dye color of antifreeze has nothing to do with antifreeze formula or performance. Chrysler’s G-05 contains orange dye to distinguish it from a yellow dye antifreeze previously used. Other users of G-05 have yellow or even blue dye. However, GM DexCool, a purely organic acid type, also has orange dye, and this has been a source of service industry confusion. Fiat’s OAT, although a different formula, also has orange dye and it has been used in early production of the Dodge Dart. The new Chrysler OAT, however, will have a purple dye."

It's far more important to use distilled water, which is less than a dollar per gallon and often overlooked in this discussion. Tap water contains minerals you don't want.

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I don't know if it is the same in the states, but over here there are two totally incompatible types of coolant - OAT (usually red) and MEG (usually blue). Using the wrong sort can cause corrosion issues and leaks (especially using OAT in a car designed for MEG), and mixing the two results in a rather nasty sludge. However, most cars in the past decade or so have used OAT.

I can't therefore see how they can sell a coolant that claims to be compatible with ALL cars, unless things have been different over there?

Another thing to watch out for is that if your car is still under warranty, they may refuse to pay out if you have a leak and have used a non-approved fluid in the car.

I personally tend to use whichever brand my local motor-factor has in stock at the time, but always make sure it is the right type - but then all of my cars have been fairly old, and from before manufacturers started trying to insist that you used their own brand coolant!

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USA has 3 colors. Red, Green, and Orange. The Prestone "works anywhere" is green, but is supposed to work will all of the above. No blue here. –  Brian Knoblauch Jun 23 '11 at 17:38
    
@BrianKnoblauch: The Honda coolant I'm talking about is blue. :) –  endolith Oct 16 '12 at 19:20

From FAQ section of Prestone Website:

"Some European automobile manufacturers request that a phosphate-free antifreeze be used in their vehicles. This issue is related to the extremely high mineral content of the water in Europe. If you were to mix an antifreeze that contained phosphates with the type of water they have in Europe, it may produce deposits that can settle in the cooling system and promote corrosion. However, in North America we do not have this type of water problem. Typical North American coolants have contained phosphates (which is part of the corrosion inhibitor package) for many years. Therefore, the question of phosphates is a non-issue here in North America. Prestone® Antifreeze/Coolant is completely safe for use in both foreign and domestic vehicles. For those consumers who would feel more comfortable using a phosphate-free antifreeze, our Prestone® LongLife® Premixed Antifreeze/Coolant and Prestone® Dex-Cool® Premixed LongLife® Antifreeze/ Coolant formula’s are phosphate, silicate, and borate free. These coolants use a special chemistry and technology that extends the life of the corrosion inhibitor package so that it lasts for five years or 240,000 kms (whichever comes first), and is safe for all cars and light trucks (old or new). Prestone® Dex-Cool® Premixed LongLife® Antifreeze/ Coolant has been approved by General Motors under their DEX-COOL® specifications and is compatible with other DEX-COOL® approved coolants. * DEX-COOL® is a registered trademark of General Motors Corporation."

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I find it hard to believe that they can make a generalization like that about the mineral content of water supplies across the entire continent. –  endolith Oct 16 '12 at 19:17
    
Also, isn't this only relevant when you mix it with tap water yourself? –  endolith Oct 16 '12 at 19:39
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Mixing coolant with tap water is never a good idea. Just spend the 50 cents and get a gallon of distilled water at the store! –  Brian Knoblauch Oct 17 '12 at 11:05

Just beware of using a formula containing silicates in Japanese engines, this can cause water pump seal failure. Use distilled water. Do not use “de-ionized” water, it will scavenge ions back from your engine metals causing corrosion. Most cars after 1998 that don’t have copper/soldered radiators can use Organic Acid Technology (OAT). If your car is older than that — beware, the organic acid can corrode away the solder.

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Deionizing water is just a cheaper way of removing salt ions to approximate distilled water. The only difference between deionized and distilled is that deionized has more non-ionic contaminants like organic stuff and bacteria. I don't believe there will be any differences as you state. –  endolith Jul 1 '13 at 15:24

Most answers here are wrong... whatever you do with your coolants, the last you can do is cause corrosion. All the formulas will prevent corrosion.

The issue is with mixing coolants you can "milk" or "clog" them. That happens because the chemicals they use may interfere with one another. The problem is ALWAYS caused by the DEX ones. They added new stuff to prolong the life (they started to market one coolant flush every 100.000 miles!) and that damn stabilizers is what will clog your coolant lines if you mix it with posphate and some other kinds.

If you clog your lines, the least of your worries will be corrosion! you will melt your engine much earlier than that!

So, the only sane thing to do, as most manufacuters do not even list the contents of their coolants, is to stick with the same that's in there. And do not do that by color. Color means nothing. There are several ones that do not play along and are the same color.

For example, i just bought a gallon of the autozone or prestone "goes with everything" (though they still write in small letters on the back "does not go with everything, check your manual") which is orange, just to find out my car had some chrysler golden thing in there. I don't remember the names and details as it was 6mo ago, but after a small research on bob is the oil guy forums, i found out i would clog my system if i mixed them.

The bottom line is, if you mix you risk it. the chance nowadays are small. VERY small. but it's still there.

If you love the car, write down the coolant you are using (brand and chemical contents) and use only that type. If you have no idea what's in there, flush, put new one, and WRITE down what you used. do not believe in color. Also, refuse to buy anything that does not have a list of 'ingredients'.

Now, for the performance, they are exactly the same thing. so, if you flush before, you are safe! you will NEVER damage your car if you use only one brand, whichever it is. regardless of what the manufacturer suggest. In fact, if you don't live in cold climate, you can use only distiled water and be done with it! (you just will have to top off every hour as most of it will boil and escape the pressure valve :) so don't do it ... but you will still get ZERO rust.

Now what to do if your level is low and you have to top off?

unless it's more than a gallon, and you never did it before, use distiled water. ALWAYS. only distiled water. It's the safest bet. your fluid now is 50/50 coolant and water. you are fine if you keep that mix from 30/50 to 70/50. so adding a gallon or so is totally fine!

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I've read all the DexCool stuff for my old Chevy Cavalier and it's all hearsay with no concrete proof of anything –  endolith Jun 12 '13 at 13:35
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@endolith more info here en.wikipedia.org/wiki/Antifreeze#Traditional_inhibitors –  gcb Jun 12 '13 at 17:09
    
Yes, but that says the problem is actually the caps and recovery bottles that were introduced at the same time. –  endolith Jun 12 '13 at 19:34

All this discussion and no definitive one way or another.

Obviously the auto manufacturers have there arguments and everybody else has there opinions.

If Prestone 50/50 extended life is Phosphate, Silicate, Nitrate and Borate f ee and uses demineralized water and is based on OAT and HOAT technoledgy of today, then there really isn't a problem here, is there??

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