Last night my daughter was driving back to BCS and the Tahoe started to overheat in Bastrop. She pulled over and checked under the hood to find that a plastic connector on the heater hose had broken. A seemingly common GM problem due to poor design, but I digress.

Today I replaced the heater hose and didn't think twice when I filled it with 3 gallons of Peak 50/50 long life green antifreeze (yellow cap on the gallon jug). Capacity is about 16 quarts so I essentially added 12 quarts of the Peak stuff to the approximate 4 quarts of DexCool that was in the block.

Is this mix going to cause problems later? Flush and go back to Dexcool, flush and go with pure 50/50 green or just leave it the hell alone?

I'd do 2 flushes ASAP, they don't mix well at all. Either coolant works okay, I wouldn't use Dexcool in a leaky system.

https://www.cartalk.com/content/i-have-question-about-antifreeze-many-months-ago-my

Don't post links to bad info

Been doing it for years. Never noticed a problem, though by now the Dexcool is probably diluted to the point it is effectively gone.

It's probably better not to mix as I think the universal causes the Dex to lose its corrosion inhibition as I understand it. Just the universal alone is fine though.

silverado_lover said:

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Don't post links to bad info

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RAY: The experts we spoke to at SAE (the Society of Automotive Engineers) said that you can mix up to about 15 percent traditional coolant in your OAT coolant before you have any real effect on the corrosion inhibitors. So if, for example, you just top up your OAT coolant with a few cups of traditional stuff, nothing's going to happen. But if you go beyond that 15 percent threshold, then it makes sense to EVENTUALLY drain out the coolant and fill it up with all one or all the other.



So this is all wrong?

silverado_lover said:

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Don't post links to bad info

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and from another rando google search.

https://www.quora.com/How-quickly-do-Green-Ethelyne-Glycol-and-Orange-Dex-Cool-Coolants-react

It seems like the consensus is that it lowers the lifespan that you'd want to keep it in the vehicle due to the mixing of corrosion inhibitors, but I haven't found a case when it causes gelling or a system problem.

Im not an expert though, so if you have a case or personal experience, please share.

We can post links with contradicting info all day brah

http://ricksfreeautorepairadvice.com/causes-dex-cool-sludge/
https://www.autoblog.com/2009/12/28/coolant-color/

GM says that the service life of Dexcool is reduced to 2 years when mixed with the green, but they also say the below.

Quote:

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If contamination occurs, the cooling system must be flushed twice immediately and refilled with a 50/50 mixture of Dex-Cool and clean water to preserve the enhanced properties and extended service interval. If you use the proper coolant (Dex-Cool) you do not have to add inhibitors or other popular additives, which claim to improve the system. These can be harmful.

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Otherwise, there are countless instances of people on the internets claiming issues when mixed. I've never mixed them for sh*ts and gigs to see what would happen myself.

If OP is willing to risk sludging up an engine and entire cooling system, neat.

In the past, I mixed Prestone with Dex-Cool with poor results.

Thankfully, nothing catastrophic, but cleaning out the system was a beatch.

Don't do it.

As recommended, flush your system twice, and fill with one or the other.

I wouldn't use the Dexcool at all. It's known to cause problems with plastics in certain cars. Flush and refill with generic, and just do bi-annual maintenance.

CDUB98 said:

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In the past, I mixed Prestone with Dex-Cool with poor results.

Thankfully, nothing catastrophic, but cleaning out the system was a beatch.

Don't do it.

As recommended, flush your system twice, and fill with one or the other.

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X2

From personal experience, Dex and green stuff don't go well together.

You could mix the "all colors, all types" with Dex, but if Dexcool (or a store brand equivalent) was available, just roll with that.