I am running low on coolant and decided to do a little research through old postings. Hopefully, one day other/new forum members may find this information helpful.

I found different opinions about engine coolants. Many people who have bought used cars and are running low on coolant are curious about the types/brands of proper coolant for their vehicle. Often, there is limited or no information about the type of coolant used by the previous owner(s). High mileage (~85k) maintenance is associated with replacing the timing belt and a system flush is especially recommended after TB job.

After all, it seems that there are two main things about the coolant dilemma:
[blockquote]1) Do not neglect your temperature gauge and regularly check your coolant level. Running low on coolant may cause leaks and air bubbles in the system which may result in quick overheating.
2) Try to use the same type/brand of coolant. If you are low on coolant and at the same time unsure of what is currently in your system, then go ahead and do a regular flush. After that use whatever you decide.
[/blockquote]
Common choices:
[blockquote]1) Generic green coolant
2) Peak coolant
3) G12
4) Universal yellow antifreeze (DO NOT USE)
5) Plain distilled water
[/blockquote]
It is recommended that you DO NOT mix different types (colors) of coolants mainly because of the acidity level and possible chemical reactions which may occur in your system. High acidity may shorten the life of your houses. If you want to check your coolant mixture then “get a coolant meter from a parts store for 6 bucks and check” by Cheese Eater.

Random coolant related quotes:
[blockquote]“If you put peak or that other green crap in it [basically, if you mix], your system will become gel. You know 1/2 of the coolant system is, wait for it.... WATER, go to your super market, & pick up a gallon of Distilled water for $1.50” by 2k S4

“not uncommon for the [coolant] pump to be leaking” by i3uddha

“First of all audi's don't use antifreeze, you can only use the factory coolant” by auditech79

“After I did my timing belt i used water only(no coolant) for a few days with no issues and have since put in generic coolant” by wemmington

“…in the end coolant is coolant regardless of brand” by Trey25

“'I’ve just been getting sick of buying gallons of G12 for $20 a pop” by a4sport

“i believe the g12 changes color from red to brown when another kind of coolant is mixed with it” by PKSJeter
[/blockquote]
Related/interesting links:
[blockquote]Replacing coolant
https://www.audiforums.com/m_562798/tm.htm

Some Reasons To Avoid The Low-priced Green Stuff
http://www.asashop.org/autoinc/october/techtips.htm

Choosing The Right Coolant
http://www.popularmechanics.com/how_...e/1272436.html

Audi Monthly Maintenance
http://www.autohausaz.com/audi-auto-...intenance.html

Timing Belt/Tensioner FAQ/Water Pump and Thermostat replacement
http://www.audiworld.com/tech/eng35.shtml
[/blockquote]