Correct Coolant in your BMW, Mercedes, or Audi - M-Spec Performance

Does the type of Coolant really matter? Short answer is YES!!!

This is a topic that comes up almost everyday here at M-Spec Performance. Questions about auto repair happen everyday but we see so many vehicle that come through our shop with the incorrect coolant in their system. We wanted to write a short article explaining some of the finer details of using the proper coolant in your high performing German vehicle.

What is coolant and what does it do?

Lets start off with a simple definition of what coolant does for a vehicle. Coolant like the name states cools the engine by lowering the freezing temperature of the water and increasing its boiling point. The active chemical is ethylene glycol. The other key function of coolant or anti-freeze is lubrication. Coolant lubricates any moving component it comes into contact with like the water pump. Without coolant and just straight water, you could have a waterpump bearing failure prematurely due to inadequate cooling.

So what about this incorrect coolant?

In this example we are going to talk about BMW however this really applies to Mercedes or Audi as well. All vehicles serviced at M-Spec Performance get a complimentary visual inspection. Part of our visual inspection is to inspect the quality and level of the coolant. One of the key things we look out for is color. For BMW and Mini Cooper the color is blue. It is also blue for Mercedes. Audi and Volkswagen for most model years use G12 coolant which is a purple color mostly. What we see a lot of times is what we call “the green coolant of death.” Usually it is a dark green color due to mixing with pre-existing blue coolant.

Many auto parts chain stores will sell you green coolant as their information system indicate that this is the right coolant for your vehicle. Please remember that these are not places to seek expert advice and green coolant is absolutely not the right stuff for your vehicle.

What is so bad about green coolant?

Green coolant contains other chemicals such as phosphate which can damage internal engine components such as the engine block, head gasket, cylinder head, and specifically coolant passages in the engine. Over time incorrect coolant can wear away at aluminum which can cause irreparable damage. During many cylinder head gasket service jobs over the years we have seen the metal eaten away which rendered the cylinder head useless. This resulted in costly repairs. BMW coolant specifically is phosphate free and that is why it is recommended for BMW by BMW.

How do I check if I have incorrect coolant?

The good thing is that is very simple to check the coolant in your system. For illustration purpose look below at the engine bay of this BMW. Circled in red is the coolant expansion tank. Mercedes and Audi Volkwagen should have the coolant tank in a similar place. Generally you can also read the top of the cap which will give an indication that coolant goes into that tank. Open up the tank while the car is cold. If you attempt to open the cap while the vehicle is hot you may release a lot of pressure in which hot coolant may burn you. Please exercise caution.

What should I do if I have green coolant in my system?

If you opened the cap and detected green coolant it is time for a full system coolant flush. The conventional method of flushing a system is to open up the radiator drain plug and the engine block drain. Unfortunately this method only releases some of the coolant and not all of it. Without a pressurized method to exchange all the coolant this will only do half the job. At M-Spec Performance we use a Robinaire coolant exchanger to perform the service. We generally fill up the machine with 4 full gallons of BMW coolant (if it is a Mercedes or Audi VW we always use factory specific coolant). We then connect the coolant exchanger via a radiator hose. The process takes about 45 minutes to 1 hour however within that time the coolant is completely replaced.

Do I have to have a coolant exchange service done often?

The answer to that question is yes and no. Coolant is unlike an oil change where it is expected to have performed every 5,000 miles or so. Coolant does however have service intervals albeit a little longer. It is factory recommended by BMW, Mercedes, Audi, Volkwagen and MINI Cooper to exchange your coolant every 2 years or 24,000 miles. Over time coolant does get dirty and can lose its coolant properties. We normally recommend our clients to perform a coolant exchange service before the summer or winter. Extreme weather can cause accelerated conditions for overheating or under cooling.

I hope this little primer has helped you understand the importance of coolant and proper maintenance. Feel free to give us a call or contact us in any way if you have any questions.

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Written by M-Spec Performance