Originally Posted By: Audi Junkie
The "mixing" of coolants is the most overblown issue on this website and on others too.
Everything you need to know about coolants is here on this page:
http://www.aa1car.com/library/2004/us120426.htm
I still have yet to hear a *reason* coolants can't mix.
Audi, that Larry Carley article does NOT recommend mixing different coolant chemistry. He says it is ok to top off different coolants with UNIVERSAL coolant. There's a difference. That article is aimed at service garages wanting to consolidate their inventory, not maximize cooling system life.
In this Larry Carley article, he reinforces these concepts:
http://www.aa1car.com/library/coolant.htm
"
GM warns that intermixing extended life coolant with ordinary coolant reduces the coolant's life to that of the ordinary coolant."
"To reduce confusion, several antifreeze suppliers (Peak and Prestone) now sell a "universal" type of antifreeze that is compatible with all types of antifreeze and all makes and models of vehicles.
Some argue this is not entirely true, but the stuff
seem to work okay and is widely accepted in the aftermarket."
"When adding or changing coolants, therefore,
the best advice is to follow the recommendations of the vehicle manufacturer.
Replace same with same, if possible, using the same type of antifreeze that was in the system. Or, use a universal coolant that is approved for ALL applications.
Regarding your last statement, in this article, Paul Weissler gives one reason
NOT TO MIX COOLANTS:
http://findarticles.com/p/articles/mi_qa3828/is_200408/ai_n9453107/pg_3/?tag=content;col1
"Sure, for small top-ups or in an emergency situation, it doesn't matter-use what you have. However, there are possible problems with extreme mixtures. An example cited by one coolant chemist: A somewhat diluted mix, perhaps 50% to 60% water, with the remainder (from top-ups) a 50-50 combination of an OAT and a conventional American coolant or a G-05.
A remaining inhibitor (borate) could attack aluminum if the silicates are depleted."
I, too, would like scientific results showing the results of mixing coolants. Until then, I will err on the cautious side based on the best info available (not anecdotal stories on BITOG, including mine).
Here's Ford's position on universal coolants:
http://www.search-autoparts.com/searchau...e/detail/329982
Just their opinion, mind you:
"Based on blind laboratory ASTM testing performed in duplicate, two leading "universal" coolants currently in the marketplace did not meet the extended D2809 requirements of Ford's Motorcraft Premium Gold Engine Coolant specification, WSS-M97B51-A1."
"Use of non-approved "universal" coolants may lead to eventual engine damage or failure. Problems caused by use of non-approved "universal" coolant may not arise immediately, but may occur over longer periods of time due to additive compatibility issues."
