This information below is from the General car FAQ forum... take a look around and read some... there are some great write ups there...
All information and facts can be found at the links towards the bottom of this writing. Thanks to all the sites that expose all of this information!
There are many types of coolants out there. With many different ingredients. Which one do you choose?
Well, pretty much everyone will tell you the same thing; "Use Only BMW Coolant".
BMW did a lot of research in the early 1990s with antifreeze/coolant due to a overwhelming occurance of plugged up coolant systems. (not allowing the coolant to circulate properly) They found this problem to be a result of silicate gel precipitation.
Many people think that all cooling systems are the same, except some are methanol based and some are glycol based. Not exactly! In newer cars, silicates are needed to protect aluminum engine parts and radiators from corrosion. The last sentence was false.
Eventually silicates are meant to drop out of the coolant mix. Only at a controlled rate. BUT over time the mixutre of chemicals and impurities and corrosion by products in a cooling system can start to hinder the performance of the cooling system. When silicates begin to drop out too rapidly, they build up and form a gel.
The most common inhibitors, the silicates used for aluminum protection, are used up faster than others. That is why some new cars (all General Motors, Mercury Cougar, VW/Audi and BMW models) have red or orange antifreeze with a new class of inhibitors, called organic acids. Examples of U.S. brands with these organic acids: Havoline Dex-Cool and Prestone Extended Life, both recommended for five years or 150,000 miles.
Silicates can be abrasive (such as beach sand) or lubricious (such as hydrous magnesium silicate - talc). Soluable silicates are made, e.g., by reducing silicon dioxide, SiO2 (sand) into SiO4[-4]. (Throw in the caution of your choice.) So, presumably, the reverse can happen, meaning SiO4[-4] will be oxidized in SiO2. So, the water soluble silica ions in your green coolant can oxidize into rather non-soluable, and abrasive, sand. (Though, making sand by oxidizing silane (SiH4) is a hell of a lot more fun.)
Phosphate is the most ubiquitous and most controversial inhibitor. It is a well known inhibitor of ferrous metal corrosion, hence trisodium phosphate is used to clean off sheet metal. American car manufacturers have specified phosphate in coolants because it is highly effective at preventing cavitation. Europeans specify non-phosphate coolants because phosphates have a propensity to precipitate in hard water. Also, phosphates have a negative effect on the corrosion rate of aluminum.
Another function of the coolant is to raise the viscosity (thickness) of the coolant mixture. Higher viscosity mixtures will reduce cavitation at the water pump. Propylene Glycol (orange stuff) and Ethylene Glycol (green stuff) will both raise the coolant viscosity, methanol will not.
Ok, now that we know a little about the coolant it self, what can we use?
A very short answer would be, a nitrates, amines, phosphate and silicate FREE coolant. Off the top of my head, Zerex G-05 meets that protocol. Made by Valvoline. Another is Caltex (petrol/gas supplier).
And what do we mix it with?
De-Ionized water is pretty much just H2O...not much else.. DI water will try to return it it's natural state prior to purification. Over time it will leach minerals from whatever it comes in contact. I have seen DI in running through PVC pipe with the pipe becoming so brittle that it would break with very little external help. Did someone ask for a litmus test? DI water left standing long enough will actually go from a pH of 7 (neutral) to 4 (acidic)....I've already done it for you. Now the real question...is DI & distilled water the same? then...antifreeze kind of throws a wrench in the mineral debate.
The minerals in your Perrier were once rock that the water simply dissolved over time as the water tried to reach an equilibrium with its surroundings. A radiator is no different than an underground cave to the water. The fact that distilled water has no minerals in it simply means it has more "dissolving potential" since it is further out of (electrical charge) equilibrium with its environment than more mineralized water would be. The exception: most coolants include corrosion prohibitors that should, in theory, prevent this kind of action. However, they may not work well in protecting the metal from corrosion caused by highly energetic DI water.
So, it seems distilled water would be the choice.
So we now have distilled water with a nitrate, amine, phosphate and silicate FREE coolant.
Next question; whats a good ratio in the water/coolant mixture?
There seems to be a very good understanding on the web that a 50/50 mixture is pretty much a good mix. Some even venture to say that 70/30 being a good one for a more hot climate. That being 70 percent water.
So, you have a mixture of 50/50 of distilled water with a nitrate, amine, phosphate and silicate FREE coolant.
There you have it. A researched water/coolant mix for your BMW. I will add more later as I find more here and there. http://www.pentosin.de/eng/products/...ntifreeze.html http://www.angelfire.com/ia2/vmax/coolantnotes.htm http://faq.f650.com/FAQs/Coolant_Change_FAQ.htm http://auto.howstuffworks.com/cooling-system1.htm http://www.circlebmw.com/service/arteries.html http://www.bimmerfest.com/forums/arc...p/t-46962.html
If you have any questions... please feel free to PM me.. or IM me... my screen name is M3alpine97.