FAQ: Dexcool / Coolant / Antifreeze Types

Mixing the two isn't going to hurt anything. Your instructor needs to be instructed......

As AA said, just don't leave it in there forever......

I disagree. The web is full of stories of congealed mixtures.
More importantly, here is what ChevronTexaco has to say on their own Havoline Dex-Cool web page:

As Aaron said:
*Compatible with conventional antifreeze. Dilution with conventional antifreeze will reduce extended life benefits.

BUT:
*Chevron recommends that this product not be diluted by more than 10% with conventional coolants.



I say flush it and refill with the yellow/amber "mixes with anything" long-life stuff...

Maybe they are trying to say if you dilute with 10% or more green coolant, you won't get the promised 5 year service life? That's sort of the whole point of DEX-COOL, so it makes sense they would tell you not to mix for that reason. Do they say anything about congealing of mixtures?

I initially had a full system of green etheline glycol, but after replacing the lower radiator hose much of it drained out. There was green coolant left in the block and heater core, the rest is now dexcool. I imagine this is somewhere in the ballpark of a 50% mixture of dexcool to green coolant. I poured just under a gallon of 50/50 Dexcool/distilled water directly into the radiator to refill.

On a side note-

When replacing the lower radiator hose or draining the coolant from the radiator, there are 3 metal clamps where the hose connects to the radiator. There is an approx 3-4" long male-male piece on top of which the lower radiator hose and the rubber fitting coming out of the radiator come together. Be sure to have a clamp on top of both the hose and the fitting coming out of the radiator. Putting only one clamp on there allowed the hose to become detached from the radiator. This happened Friday night as I was driving through heavy traffic in downtown Asheville taking my girlfriend out to dinner.

That small section of tube can be eliminated and just put your lower hose directly on the radiator nipple.
This reduces the amount of joints that can fail, as you have found out.

That 3" - 4" male nipple was used during production just to make the initial install of the radiator easier for them.

There is no P/N for the small section of hose that you would have to replace if it failed.

When I put new hoses on the car I just eliminated it completely. The replacement hose is long enough to make up the difference.

So next time you have to remove the hose, I would recommend removing that short section completely and eliminate the extra joints and clamps.

This is from GM TSB #00-06-02-006D. I didn't post the whole thing cause it's irrelevant to what we are discussing, but I think this is what AA is looking for. It says nothing of congealing mixtures, only lessening the service life of the DEX-COOL.

I pretty sure it doesn't congeal when mixed, but Mark was onto something posting the warning from Chevron. I did some digging and turns out there may be another good reason not to mix DEX with green coolant. It has to do with the types of corrosion inhibitors used. Apparently when you mix, the resulting corrosion resistance isn't as good as when you use only one of the types.

Here's some more specific info from U of Tennessee's Agricultural dept:

"An alternative to tradition green antifreeze is a product currently used by many engine manufacturers. "Orange" antifreeze is a long life or extended life type of antifreeze used to increase the useful life of engine coolant. It is ethylene glycol base as is the green antifreeze. The difference between the two colors is that orange antifreeze contains a different type of corrosion inhibitor that has a much longer service life than silicates, phosphates and borates. Orange antifreeze contains organic acids that protect engine parts from corrosion. Silicate (green) type antifreeze does not mix with orange type antifreeze. Never mix the two colors in a cooling system. The organic acids in orange types will cause precipitation of silicates in the green type and corrosion protection is greatly reduced.

Over time, the corrosion inhibitors will be depleted and the corrosion protection is lost. Aluminum is especially vulnerable to corrosion and many vehicles have heads, radiators and other aluminum components in the cooling system.

Orange type antifreezes are good for five years or 100,000/150,000 miles in newer vehicles (1996 and later). They can be used in many older vehicles (ask your vehicle dealer if it is safe to use orange antifreeze) if all of the green mixture is flushed from the system and is replaced with the orange mixture. Useful life is about four years or 60,000 miles in older cars."

Link: http://bioengr.ag.utk.edu/Extension/ExtProg/Machinery/Articles/engcool.htm

^^^^^ All of the above does not mean mixing coolant types will congeal. I think what happens in most cases, there is another problem the owner is unaware of, like oil seeping into the coolant, an overheating issue, or an improper ratio of coolant to water that causes the DEX-COOL to gel. Then they find out someone added some green stuff at some point, so they blame it on that. Another prime cause imo for congealing coolant is that many DEX-COOL users simply don't change it when it's 5 years old. 5 years is a long time, and to some that means 7, 8 or 10 years, or forever. They never change it, then they finally switch over to green stuff and problems occur. Well it must have been the mix, not the fact that they ran the DEX-COOL far too long. The damage was already done before they switch or mixed, they end up with gelled coolant or "sludge", and attribute it to the wrong cause.

rivman96 wrote:

Shortly after finishing a coolant flush at school, my teacher walked by and realized I was dumb enough to mix red dexcool and normal etheline glycol. It is my understanding that the mixture can congeal. How long do you guys think it is safe for my riv before flushing it again? I wont be able to get my car into the shop at school again for a week, and I have to do a good amount of driving for my job. Perhaps I am better off paying a shop to do a flush? Thanks

Aaaahhh. You do need to change it but it's not a fire.

Schedule yourself into the shop for next week, then flush and refill with either Dex or conventional or the new 100,000 mile mix-with-any.

The mix-with-any is dexcool with a different color dye and compatible corrosion inhibitors to the regular green stuff.

Suggest you consider putting a tag on your overflow bottle or write on it with a sharpie the mileage you did this flush at and what's in it (dexcool, conventional, or extended life mix-with-any). Avoids confusion.

And oh by the way if you're mixing the coolant yourself I suggest you use deionized or distilled water to avoid mineral contamination of the coolant.

Albertj

Within a week of buying my riv, I flushed out the shitty dexcool stuff with good old fashioned green.
A coworker bought a brand new 2009 Grand Prix, and after a year, it was building up the orange mud on the radiator cap and in the top of the radiator. He never mixed it, he treats that thing like his baby.

Actually, I think there's another theory that the "OAT technology" in the Dex also caused sludge/deposits to form if air (or exhaust gas) got into the system...

EatDirtFartDust wrote:

Within a week of buying my riv, I flushed out the shitty dexcool stuff with good old fashioned green.
A coworker bought a brand new 2009 Grand Prix, and after a year, it was building up the orange mud on the radiator cap and in the top of the radiator. He never mixed it, he treats that thing like his baby.

They never made a 2009 Grand Prix for one, and for 2, it was sand in the block casting or a fuct LIM gasket that caused that "mud" within a year. DEXCOOL does not sludge on it's own. It's a myth, a farce, a falsehood. This myth lies in the same category as "you can't mix Synthetic and Conventional oil"..............

According to wikipedia:

"DEX-COOL specifically has caused controversy. Litigation has linked it with intake manifold gasket failures in General Motors' (GM's) 3.1L and 3.4L engines, and with other failures in 3.8L and 4.3L engines. Class action lawsuits were registered in several states, and in Canada, to address some of these claims. The first of these to reach a decision was in Missouri where a settlement was announced early in December 2007.[15] Late in March 2008, GM agreed to compensate complainants in the remaining 49 states.[16]

According to the DEX-COOL manufacturer, "mixing a 'green' [non-OAT] coolant with DEX-COOL reduces the batch's change interval to 2 years or 30,000 miles, but will otherwise cause no damage to the engine."[17]

According to internal GM documents[citation needed], the ultimate culprit appears to be operating vehicles for long periods of time with low coolant levels. The low coolant is caused by pressure caps that fail in the open position. (The new caps and recovery bottles were introduced at the same time as DEX-COOL). This exposes hot engine components to air and vapors, causing corrosion and contamination of the coolant with iron oxide particles, which in turn can aggravate the pressure cap problem as contamination holds the caps open permanently.[18]"

At 134,000 miles, my LIM has yet to be replaced. It is certainly on my to-do list. I wonder if Dexcool legitimately does corrode GM's LIM gaskets, or if GM may have blamed Dexcool for their low-quality gaskets?

If the Coolant was to blame for any of this, they would stop using it! They wouldn't come out with an updated LIM set.....If GM had a shred of proof that DEXCOOL had anything to do with failing gaskets, DEXCOOL would be gone, and all those V6's would be recalled for new gaskets and a coolant flush. You never hear anything about 4cyls or V8's having failed coolant gaskets because of DEXCOOL, yet they all use it. GM probably compensated those people just to shut them up. Everyone has to blame somebody......even if you have 130,000 miles and haven't done a shred of maintenance (I don't mean you specifically). It's always "their" fault

The MAIN thing to learn from this is.....take care of your damn car and it will take care of you. If you mix the coolant types, get the shit flushed within 2 years....simple as that. People all too often have a coolant leak somewhere, and they "top it off" with whatever they get the cheapest, regardless of what is supposed to be in the car. 2 or 3 years later, without getting the original problem fixed, they now have a $1000 repair, and don't know why

GM stands by DEXCOOL. And still, to this day, recommends it's use ONLY.