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Dex-Cool mixed with Ethylene Glycol

Can Prestone Dex-Cool be mixed with your basic NAPA Ethylene Glycol? My NAPA guy sold me the Prestone saying that that was the Nissan recommendation for my 2001 Frontier. I’ve got about a 50/50 mix in my truck now but friends tell me hat I have doomed my cooling system. Huh? What did I do wrong? Must I bring it in immediately for a flush?

I would strongly suggest a flush. If you get it out of there fast you will be ok. A quick google search will reveal that dexcool is very temperamental and should never be mixed with other kinds of coolant.

Why did you top it off? Do you have a leak? If so you should repair it, as air pockets in a dexcool system will result in a rust powder sludge problem. Another question; are you sure your nissan came stock with dexcool? Check your owners manuel for the fluid specification.

Orange Dex-cool is standard for some GM models. I never heard of Dex-cool in a Nissan Frontier. Did someone talk you into using it? Are you confused, because some Japanese imports use a red (or pink) coolant that is silica-free. The red coolant is compatible with green Ethylene-Glycol coolants. No problem, there. When was your last cooling system service (a flush and fill) done? Who did it?

Just thought it would be useful to drain & refill new before winter. Hasn’t been done since I’ve owned the truck - nearly 5 years. Trying to stay ahead of problems. No current leaks. Owners manual doesn’t specify except to say Nissan coolant. NAPA guy sold be the Dex-cool saying that was the recommended coolant. So much for a cheap DIY solution. That’s why I’m a carpenter & not a mechanic.

See reply above. This Prestrone product is orange. What was in my system was green. Don’t know if the green was original. 104,000 miles now, so I thought giving the system some new juice would be prudent. Friends - after the job - tell me that mixing the two will lead to problems. A search of the Car Talk threads suggest mixed thoughts on the subject but as most posts are quite dated I thought I’d ask for 2010 thoughts on the matter. Have I created a problem that needs an IMMEDIATE solution or am I good for the winter? Carveaholic seems to believe that I shouldn’t wait. Thank you both for your feedback.

I commend you for being proactive about maintenance. I have a GM vehicle and, long story short, had to do an extensive repair to the front end, I temporarily mixed Prestone green (says its good for any color) with the factory dex ( I was gonna have to drain it and fill it to complete the repair). Less than four months later when all the repairs were done I spent the extra money to flush and fill with factory dex. I get paranoid about fluids and always use factory spec. NOTE: Not always OEM, but it MUST IMHO meet the spec.

I think you should drain the coolant, flush the system as well as you can, then refill it with fresh anti-freeze. I prefer the standard green stuff unless the owner’s manual specifies otherwise. I’ve never heard of Dexcool in anything other than a GM product.

Everything I’ve heard is that Dexcool cannot be mixed with other coolants, and that it’s possible to end up with a gel, which is not a good engine coolant.

I’d err on the side of caution, and I’d do it soon. As Carveaholic, suggests, Google Dexcool and read all about it. You won’t want it in your truck after you’ve done some research.

I’d get it on a flush machine.

These days I’ve just started running “global” coolants in everything. There are a few makers (e.g. Peak; Autozone has one under its name). Its yellow and says it mixes with everything. I don’t care much about the mixing - each time I’ve had the cooling system on one of my cars emptied I just go with the global. Half the time that’s what shops are doing anyway unless you say otherwise.

You are right. Google Dex-Cool & read about class action lawsuits & sludged up coolant systems & on & on.

Why is it featured on the Car Talk home page?

And so much for the words of advice from my local NAPPA guy. Guess they were trying to dump stock. Yikes, what a pain…

I did mis-read. I thought the Dex-cool was already in it, and you were adding Prestone green at the NAPA guy’s recommendation. I suggest you no longer trust that NAPA guy. And, your due for a flush and fill, so I’d go ahead and do it, and refill with good old Ethylene Glycol, the stuff the owner’s manual recommends. Dex-Cool doesn’t mix well with ANY other coolants and will sludge up your cooling system. This can turn into a very expensive repair.

Well, now I don’t see it on the home page now, but I did earlier when I started this thread - must have been a rotating banner ad. Still, why is there any advertising for it on this forum if it is such a problem child?

GM has deep pockets and a superiority complex.

You have nothing to worry about.

Mixing regular coolant with a long life coolant just makes the coolant a short life coolant. So instead of being able to go the infered 5 years/150,000 miles before the coolant requires service, the cooling system is one where the coolant should be serviced at the 3 year/30,000 mile interval.

This is just another urban legend that just won’t die.

Here’s what the boy’s have to say on the subject.


There is a lot of passionate discourse on this subject & how Dex-Cool is really “Death-Cool”. You Tester, & Click & Clack are the only cool heads (no pun intended) on the subject now that I’ve started looking. So really, really? Just relax & service again next year? Probably won’t have 6,000 miles more by next fall. I’m not heading towards a gummed up water pump, corroded gaskets & clogged up hoses by mid-February? Scouts honor?

Well, here is a slight counterpoint on this site specifically mentioning Death-Cool:

Also make sure to stay away from ‘organic based’ rust inhibitor additives. They originated in Euro/Asian markets and are not compatible with Dex-Cool. These additives may cause gumming of the antifreeze.

As for sludging and early parts failure, it is imperative that you keep the antifreeze topped off or the low fluid level will cause sludging. There is a GM Technical Service Bulletin (TSB) on this matter.

Confirms my understanding of Dex-Cool and the subsequent nightmares of too many owner’s suffering expensive repairs due to this stuff. Oddly, Dex-Cool is the only OAT coolant that is suffering these problems. Other non-Dex-Cool OAT or HOAT coolants haven’t been doing this stuff.

I can only tell you my mechanics at coolant change suggested dumping dexcool, and going with peak global, just in case there was any dex cool left as they would get along together. After reading about problems with dex cool sludging, and being associated with failing head gaskets I have come to appreciate their recommendation. I do not know why they were worried about compatibility problems, but I would guess it was from personal experiences rather than old wise (my friends wife says wive’s is politically incorrect) tales.

That was a good read - thanks. So, I’m only 50% to 60% there by that info. I did not do a complete & thorough flush - only emptied about 8 quarts of an 11 quart capacity. I did not use distilled water but I did use water filtered through our Britta. If I emptied the radiator one more time & refilled with the Prestone Dex-Cool I would still likely have some green left in the system. Is that worth doing because it is so easy to do, or a waste of more time? Or, as Mr. Tester is suggesting, all is OK as is? Thank you all for your feedback.

I’ll agree it probably won’t do anything over the course of the winter (see above post), but I still would err on the side of safety. I think the OP needs to find out if the stuff he put in actually was dexcool and not just coolant with orange dye. My cooling system is spotless, because of maintenance, and this is what the OP was trying to do. The problems start to surface when coolant level gets low, or it isn’t serviced with proper intervals. If the OP is comfortable he will remember to change out the coolant in 3 yrs without fail. I think he’s fine. I would personally get a flush as soon as it was practical (I.E.: Spring, Summer, Next week), but I wouldn’t freakout about it.

The other thing is OAT coolant can, but wont always, soften some plastics and gaskets… Another reason to use original spec.

I have nothing but respect for tester, Sorry for my big BUT, if you can work it out do a complete flush and go to peak global.

If Tester says it’s OK, then it’s OK.