Originally Posted By: artbuc
Originally Posted By: hemitruck
No
Ok, can you give a specific example of where the Napa formula would be chemically incompatible with another coolant, e.g. form corrosive by-products and/or precipitate solids?
Can I name one specific example? Not sure about that.
However, one thing I can say is that manufacturers utilize a specific chemistry for their coolants based on the physical makeup of their engines, and other associated systems (radiators, etc..), as well as the operating conditions under which their engines run. This results in a very specific chemistry for each coolant, or in some cases 'families' of coolants, such as is the case with Mazda FL22 and Motorcraft Premium Gold (G-05) coolants, which are chemically the same, just with different coloration. These coolants are both also good for 5-years or 100,000 miles before they are used up, or risk precipitating out, etc..
As far as I know, all "universal" coolants are essentially clones of dex-cool, based on the chemicals used to make them what they are. As such, if you mix them into the coolant in an engine that is already using a non dexcool coolant, you'll end up screwing up the chemistry of the fluid, and this will always negatively impact the effectiveness of the coolant, ultimately leading it to precipitate early, or potentially reduce their ability to mitigate/prevent corrosion, etc.. Instead of the coolant being good for 5 years and/or 100,000 miles (or more, in the case of Nissan, etc..), they might only be good for 2 years or 30,000 miles before they run the risk of causing problems.
That said, if you do a FULL flush so you can be sure that the previous fluid is almost entirely gone, then switching many cars to use only the "universal" stuff can potentially work fine.
I personally won't use the "universal" stuff myself. The genuine stuff is just not that much more expensive.