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Sofa King
Sofa King New Reader
9/16/08 5:51 p.m.

I recently bought a C5 Corvette. The low coolant warning came on and I topped it off with Peak 50/50 coolant. It says that it is safe to "mix with any color antifreeze". I haven't experienced any problems, but while doing other research, I discovered the discussions on Dex-Cool and its problems, and the potential problems that mixing it can cause. I am guessing that I should flush the system and replace the mixture that I have in there now. But what should I put back in? From what I can find GM is still insisting on Dex-Cool, but seems like there are a lot of negative opinions of the stuff. What do you guys think?

If this has beed discussed before I appologize in advance, I did a search and came up empty.

Jensenman SuperDork
9/16/08 7:00 p.m.

DexCool is fine, unless it gets contaminated with the green stuff. In that case, the coolant will turn brownish and muddy and lead to some serious problems. I have seen this first hand in the service drive. That means a drain, thorough flush, and then refill with 50/50 green stuff, you can no onger use the red. I can't vouch for the 'any color' stuff out there.

geoffl New Reader
9/16/08 7:56 p.m.

I just changed the Dexcool in my 02 Z06. It looked fine with good color. I just wanted it out after 6 years in the system. No problems with it at all.

WilD Reader
9/16/08 8:13 p.m.

I still have the original DexCool (I believe) in my 2000 Cavalier. I topped it of with some of that "add to any color stuff a couple years back, It still looks/tests/cools fine. Not bad for 8 years and 118K miles.

foxtrapper UltimaDork
9/16/08 8:28 p.m.

There is so much urban legend stuff regarding Dex-cool that I don't know that you can tease out what is known from what is suspected.

Be carefull when it comes to judging antifreezes by color. Dexcool is orange as I recall, red is Toyota, green is generic ethylene glycol, yellow can be generic or Mercedes I think, etc.

02Pilot New Reader
9/16/08 8:30 p.m.

The problems with Dexcool, as I understand it, stem from one of two causes. First, mixing with traditional ethylene glycol coolant causes a bad reaction; so-called universal coolants are propylene glycol and should not cause major detrimental effects, though you may lose some service life of the Dexcool. Second, it is apparently fairly volatile and does not like being used in a non-sealed system. This is not normally a problem, but GM had a bad batch of intake manifold gaskets on one of their common V6s that allowed air into the cooling system, which caused the Dexcool to turn into pudding and made many owners quite unhappy with it.

Dexcool is an OAT (organic acid technology) coolant that is apparently considerably pickier about operating conditions than HOAT (hybrid OAT) or other propylene glycol coolants. Personally, I prefer a HOAT coolant like G-05, which seems to be quite effective and stable.

P71 Reader
9/16/08 8:34 p.m.

I've swapped 2 Fords TO DexCool and I love it. The cars run cooler and stay in a more normal temperature range while racing.

curtis73 New Reader
9/16/08 8:53 p.m.

As far as I'm concerned, Dexcool is satan spawn. A decade-long study of GM owners, warranty data, and speaking with a few folks who work for GM, Dexcool is just terribly unstable stuff.

It uses any opportunity (especially around leaks or if excess air is in the system) to drop silicates out of suspension, turn to orange jello, eat water pump packing and bearings, and otherwise become acidic without warning.

GM signed a very long contract with Dexcool. On the outside they are saying what wonderful stuff it is while dropping billions on warranty repairs. Behind the scenes people are suing the crap out of GM and GM is subsequently suing the crap out of Texaco. Some links:






I could go on, but I'd just be listing a different class action suit for each state, and then regurgitating a million different forum posts. Its known to be crap, even GM and Texaco are admitting it. (see last link)

An excerpt from one of those sites:

DEX-COOL specifically has caused controversy.[2] It is casually linked with intake manifold gasket failures in GM's 3.1L and 3.4L and with other failures in 4.3L engines. Class action lawsuits were registered in several states, and in Canada,[4] 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.[5] Late in March 2008, GM agreed to compensate complainants in the remaining 49 states.

daytonaer New Reader
9/16/08 9:00 p.m.
02Pilot wrote: ....though you may lose some service life of the Dexcool. ....

This is a biggie, otherwise its alright just like the packaging says.

Now that you have regular service antifreeze mixed with extended life antifreeze, you are now on the regular service schedule. So because you have universal green stuff in there, you need to change it every year (supposed to at least..) instead of every 6 with pure extended life antifreeze.

Oh, and congrats on the vette!

ApexC Reader
9/16/08 9:34 p.m.

All right, let's go OT for a second. Educate me on the coolant color issue. Does it really matter?

Junkyard_Dog SuperDork
9/16/08 9:41 p.m.

Dexcool ate gaskets on land Rovers when they switched...but they were Land Rovers so instead of leaking at the first service they leaked ON THE SHOWROOM FLOOR! I'm a 10 year LR tech and I saw it happen more than once. Rover changed the gasket coatings and they leak normally again If I weren't worried about the seals in my older stuff not liking it I'd switch to it. As discussed when it hits air it goops up, making leak diagnosis a snap. If it goops up IN your engine its because you have other problems-Dexcool is only the messenger. As far as certain GM V6s leaking with this stuff-those motors were crap with LONG histories of coolant problems before Dexcool was even invented.

curtis73 New Reader
9/16/08 10:54 p.m.
ApexC wrote: All right, let's go OT for a second. Educate me on the coolant color issue. Does it really matter?

Colors are added mostly so you know what kind of coolant you have. Having a coolant that says it mixes with all colors and types makes the hair stand up on the back of my neck. Just try mixing green Prestone (EG) coolant with Evans (NPG) coolant and watch the mess.

Technically they are all miscible (infinitely soluble) with each other and with water, but sometimes the chemicals in them don't play well with others.

Sofa King
Sofa King New Reader
9/16/08 11:21 p.m.

Thanks for the input. Man, Reading all the posts above points out exactly why I asked the question. There are reports of ugliness combined with endorsements. Confusing as hell. I want to take the safest route possible to avoid future disasters. I don't mind shorter coolant life as long as there aren't other negative impacts of non Dex-cool coolants on the LS1.

John Brown
John Brown SuperDork
9/17/08 7:10 a.m.

Go to the Texaco DexCool bottle read the ingredients, then read the ingredients of green ethyl glycol and read. There are two different sodium based additives that make the Long Life version different.

The problem is that DexCool is not the only player on the block, add proprietary formulas for Ford, Chrysler, VW and others and there are a lot of EG and PG based formulas sitting on a bunch of shelves right now.

Jensenman SuperDork
9/17/08 7:27 a.m.

As long as you thoroughly flush the cooling system of any DexCool residue you should be all right. Make sure to completely drain the cooling system, flush with straight water, then use a chemical flush with straight water. Rinse thoroughly again and then refill with green stuff.

ignorant SuperDork
9/17/08 7:30 a.m.

I used it in my wifes saturn. It was ok. noticed some sludge when the water pump went, and continually had minor problems with heating and the thermostat. But being the good guy that i am.. problems never got "bad" cause I kept on top of maintenance. It had atleast one coolant flush and fill when I was around.. i think. maybe.

curtis73 New Reader
9/17/08 2:23 p.m.

After three water pumps and two heater cores in 36,000 miles, I flushed and filled with green.

Mind you, GM refused to pay for ANY of the repairs, claiming that I didn't follow recommended flushing intervals... even though the OWNERS MANUAL says that you don't even need to open the radiator cap for 100k.


belteshazzar Dork
9/18/08 10:17 a.m.

similarly GM advertises some of it's auto transmissions as "filled for life". And subsequently suggests changing the fluid every 100k miles. I found that disconcerting. Did they mean the whole transmission's service life is 100k?

John Brown
John Brown SuperDork
9/18/08 10:27 a.m.

Most of the FFL GM transmissions spit the seals out on the driver side by 50K miles and they become Boat Anchors For Life transmissions.

belteshazzar Dork
9/18/08 10:52 a.m.

Well, at least it's a total pain in the ass to check the fluid level.

Dr. Hess
Dr. Hess SuperDork
9/18/08 11:24 a.m.

So, lemme see... GM sells cars with 50K mile transmissions, and as 50K is all the life you'll get from it, there's no point in really changing the fluid anyway. They fill the radiator with stuff they got contractually obligated to buy and won't change that, placing all blame on the consumer for buying their car in the first place (curtis73, I think you should persue the claim against them on that, if you can show the owner's manual saying don't change it and they say it's your fault for not changing it). Then they wonder why the American consumer wants to buy a Toyota or Honduh. Must be because of the union workers or health care costs or something, yeah, that's it. Couldn't be a culture of "this piece of junk is good enough."

44Dwarf Reader
9/18/08 2:06 p.m.

The cobalts level drop just a smidge over the winter i didn't have any on hand to top it off so i used straight water. No more light. :)

Jack SuperDork
9/18/08 5:52 p.m.

Personally I prefer SAAB's blue coolant, for any vehicle with aluminum touching the coolant. These days I suspect every vehicle has aluminim in the cooling loop somewhere. My one GM has Dexcool, at least until I change it out.

The blue will freak folks out, 'cause we all know coolant isn't BLUE!


noisycricket New Reader
9/18/08 9:01 p.m.
02Pilot wrote: Second, it is apparently fairly volatile and does not like being used in a non-sealed system. This is not normally a problem, but GM had a bad batch of intake manifold gaskets on one of their common V6s that allowed air into the cooling system, which caused the Dexcool to turn into pudding and made many owners quite unhappy with it.

If by "bad batch" you mean "every single one of them" then yes. Pretty much ALL 3100/3400 with the "flat" intake manifold (not angled like the original 2.8/3.1 FWD port FI setup) have the plastic composite lower manifold gaskets that WILL fail with regularity.

It's not a Dex-Cool problem, either. The gaskets fail even with normal stuff. The plastic just sort of biodegrades and the rubber shifts around and it leaks. There are updated gaskets available that use metal backing instead of plastic, they aren't cheap but they don't fail every 30k miles either. (And follow the torque spec/sequence religiously!)

Note that Ford 4.2l V6s in the trucks suffer this same problem, and they do not use Dex-Cool. As a bonus, they can leak the coolant into one of the intake ports, causing hydraulic lock...

The problem with Dex-Cool is in unsealed systems, or systems that leak and get air in them, and it turns to mud, filling the heater core tanks or the radiator tanks with sludge. Blazers with no heat and fullsize trucks/vans with the whole bottom half of the radiator plugged solid with mud are quite common. I have not seen head gaskets clog 100% but i have seen them very close to plugged, so I can believe that it happens.

We "convert" systems to normal coolant, or generic longlife, all the time with zero troubles.

curtis73 New Reader
9/19/08 12:05 a.m.

Cricket has it spot on... the gasket problems were due to manifolds and gaskets, not Dexcool.

But that doesn't take away from the fact that Dexcool is junk

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