DCA4 and other additives really that troublesome? Drop out, deposits, yellow metal and solder corrosion...?

Oct 14, 2005
Schafflund, Germany
While some OEMs are moving “back” to silicate or phosphate containing coolants, some OEMs never moved away from incorporating inorganic inhibitors into their specifications or preferred coolants. Overall, it seems that the advantages of inorganic inhibitors outweighs their disadvantages as long as they can be kept in solution, which requires the coolant to be kept chemically balanced/stable. Overtreatment with SCAs is among the things that makes coolant unstable.

Thinking in those lines, having overcome my personal silicate-phobia, I do have intentions to "make my own" mixed fleet hybrid coolant by adding a standard 3 percent “pre charge” dose of Fleetguard DCA4 to a well-known and readily available European 2-EHA-free sebacate/adipate-based OAT coolant. Anybody capable of looking up an MSDS will have to agree that DCA4-liquid already has a small amount of adipate and that some of Fleetguard's DCA4-based coolants have a small amount of sebacate. Also, DCA4 getting in contact with European hybrid and OAT coolants has a long history - in many cases due to coolant filters on US engines being sold to Europe or elsewhere outside North America.

Of course, mixing different coolants in a way where each technology becomes diluted to the point at which it becomes ineffective is counterproductive, but that is not what happens here.

Because of the organic inhibitors being adequate like 99 percent of the time, DCA4 is expected to deplete at a very slow rate. I would most likely not have to add any during a 6 year, 100 kkm or 5000 hour change interval. In theory, drop out from either overtreatment or spent DCA4 inhibitors should not become an issue.

FWIW, I had a virgin sample of “my” 50/50 mix tested years ago and silicon was 115 ppm. That is about what any “low silicate” coolant has these days. Phosphorus was 1209 ppm - similar to the “old” Toyota Red P-OAT, which is too much for Prestone’s taste according to their Cor-Guard vs. others presentation. In 2015, PQIA found 1040 ppm of phosphate in Preston (still need to figure out how much P there is in PO4 , but I am too lazy to dig out my high school chemistry book right now).

Other than that, the only thing holding me back is that some SCA-based heavy duty coolants look slightly bad on paper when it comes to yellow metal and solder corrosion, especially in the ASTM D-2570 test, which may or may not tell a whole lot about actual performance in real world engine conditions….Then there is somebody on another forum reiterating how badly DCA4 eats away brass.

What is your observation with properly dosed DCA4?
Jan 18, 2020
United States
i don’t think there’s single fully formulated coolant or serious additive that actually attacks yellow metals.