universal coolant

I'd be pretty dubious regarding that, as well. It just stretches my credulity too far to think a single coolant could be compatible with all the different chemistries out there now.

On the other hand, from what I've seen old cars expecting ethylene glycol seem to do fine with just about anything EXCEPT the OAT technology (GM DexCool). That stuff will rot a cooling system not designed for it (and it's arguable whether a cooling system that IS designed for it will survive).

You don't say what year or model your car actually is; verify that it really does take ethylene glycol, and replace your Haynes with a real service manual.

NAPA still sells a bewildering array of different antifreeze formulations.

Agreed

Agreed on all counts.

They're all ethylene glycol based, except the "less toxic" ones which are propylene glycol based. The chemistry difference is in the corrosion inhibitors, not the freeze inhibitors.

DEFINITELY.

Interesting -- I'd had the impression that G05 and DexCool were based on something else. Since they're not, I find myself wondering whether G05 (HOAT anticorrosion) might not actually be useable in everything?

Well, there's a great deal of physical evidence to suggest that DexCool is based on concentrated sulphuric acid, but nope, it's ethylene glycol.

Potentially. I don't know enough about the various manufacturers' proprietary formulations to say for sure. Guess we'll know in about seven years.

I agree with everyone else that it could go either way with that "Universal" formula - you'd think Prestone would be applying several years of lessons learned, but companies can do some pretty stupid things

- after all, DexCool?/Prestone Extended Life? OAT was supposed to be the holy grail/last word on antifreeze but has been anything but.

I've been putting G05 (HOAT) in everything I own (including one Buick) as I replace the coolant. Ford and Chrysler wisely held off on the DexCool?, and the G05 was developed in answer to the problems that DexCool had. G05 is now the Ford and DC factory coolant.

Here's a very recent discussion on DI.net in which someone posted some decent e-mail responses from Prestone on the subject (BTW - I'm Peva on DI.net.):

(notice that there are two pages in that thread) They were surprisingly candid, but aren't going to go past a certain point with their info. lest they imply that a particular product has problems (a marketing/legal no-no).

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

Hmm, A clear colored universal coolant.

We could call it water. :-)

Yes, It is called Water. You mix it with Prestone antifreeze! They must have been out of it at the time.

Actually Prestone makes an OAT "All Makes All Models" formula, commonly called "Universal" antifreeze. That is what the OP was referring to. However it is, according to the Prestone web site, the traditional (green) color. Prestone markets it to the aftermarket world as being the only antifreeze you need to stock.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

That would be the Prestone "All Makes All Models", but it is supposed to be traditional green color.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

Oh, is Prestone's "everything" coolant OAT? Thought it was HOAT. No OAT in my cars -- ever again.

From their web page on the All Makes All Models: "The new Prestone® All Makes All Models Extended Life Antifreeze/Coolant is a patented Organic Acid Technology formula..."

From my reading, I had figured that the (main? only?) difference between OAT and HOAT was the silicates (none vs. some). I became a little more confused when a guy on DI.net posted the following e-mail response that he got from Prestone in that thread I referenced in my earlier post:

"Thanks again for your contact. Silicates have long been used as an ingredient in the corrosion inhibition package for automotive antifreezes. We continue to use them in some of our formulas.

"Silicates, however, are not viewed as a long lasting inhibitor so other ones are necessary for the extended change intervals that many of the car manufacturers are recommending. Antifreezes that are silicate free are not considered inferior to ones that contain silicates. For instance, Asian manufacturers have recommended and filled their vehicles with silicate free coolants for many years. If the absence of silicates in antifreeze created a corrosion protection problem, we would expect to see similar concerns with Asian vehicles as well. This, however, is not the case.

"In summary, there are both good silicate and silicate free formulas available on the market.

"We hope this has been helpful.

"Prestone"

Some of that may sound familiar to you, Daniel, from our days over on rec.autos.subaru. Subarus (Japanese in general) radiators were known for not being able to hold up with traditional green antifreeze - and in the U.S. during the 80's, that was all that we had in the stores here. The word on the street was that the special antifreeze that Subaru (and, IIRC, Toyota and Honda) dealers sold for top dollar were indeed silicate free - and the Japanese manufacturers claimed (and many owners, including me, found out the hard way that they were right) that that was the key to keeping their radiators going (much smaller tubes, clogged up much more easily).

As I've said before: Unless different information comes out, I'm sticking with G05 (HOAT) for everything.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

I've done a *little* bit of researching and snooping- just enough to be dangerous, probably :-)

For the record, as Dan Stern already posted, ALL antifreezes are ethylene glycol, except the "low toxicity" ones which are propylene glycol. The difference is in the corrosion inhibitor package.

Corrosion inhibitor packages appear to fall into three broad categories:

1) silicone/silicate and/or phosphate based. Completely inorganic. The good old "green" Prestone, as well as the old formulas of Peak and Zerex.

2) Hybrid organic acid technology (HOAT). Contains a combination of organic acids and conventional inorganic inhibitors such as silicates of phosphates. This includes G-05 (the stuff used in current-production Mopars from the factory) and also appears to be what the "universal" coolants are made of.

3) Organic Acid Technology (OAT). This is GM Dex-Crap and any coolant that "meets the Dex-Cool spec. Avoid like the purple plague.

SO what do you use in an older car? Good question!

If you're paranoid to the nth degree, your car CAME with silicone-silicate inhibitors, and you want to stick with them, then it looks like some of the antifreezes intended for Diesel engines might be the ticket.

But from most of what I've read, the HOAT coolants should be fine. They still have some silicates, but in lower dosages than the older coolants so the water pump seals should last longer. Plus they don't have the problems DexCool has. In fact, If I owned a GM product, I'd probably use one of these instead of Dex-Crap.

I think that's exactly what's going on. HOAT seems to actually be the best of both worlds, from all I've been able to dig up.

There's still no way I'm going to run ANY coolant for 5 years in an older car, but at least I'd feel pretty safe using a HOAT coolant and an annual or 2-year flush/fill schedule in my old cars.

No - Prestone claims that their "All Makes All Models" ("Universal") coolant is OAT - *not* HOAT - see my quote from an e-mail reply that was posted to DI.net in an earlier post in this very thread.

See my last paragraph below.

G-05 is approved for diesel engines - see comments below.

I agree - I put it in my wife's '99 Buick Century last year after a flush.

Regarding G-05 diesel compatibility: G-05 *IS* suitable for use in diesel engines. Zerex used to have a July/October 2003 article from Cool Profits Magazine (a trade magazine of

self described as "News, Views, and Education for the Automotive Radiator and Air Conditioning Service Industries") linked from their G05 coolant web page (they've since removed the link - too much useful information I guess - the article was titled "Coolant Color and its Significance" and written by Dave Turcotte, Technical Director, The Valvoline Company (parent co. of Zerex)). I saved the article to my hard drive before it was removed from the web page. From that article: "For the first time, light duty factory fill at Chrysler and Ford is a fully formulated nitrate-containing fluid. This makes it compatible with diesel engines, including heavy-duty, wet sleeve lined. One can use this fluid in Cat, Navistar, Mercedes, Cummins and Detroit Diesel applications. Large Diesel manufacturers have been concerned for many years about light duty fluids in their engines. The automotive change to fully formulated hybrid G-05 has resolved this issue."

From another article on the imcool.com web site: "it [G-05] meets the new ASTM D6210 specification so it can be used in diesel trucks."

For us DexCool bashers, here are a couple more CPM articles that you may find of interest:

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

Just did a Google search and found the complete Dave Turcotte article:

It is on the valovoline.com web site (which is also the Zerex web site). Don't see a way to find it from inside the Valvoline web site, even though the direct URL from Google works. Looks like Google provided a backdoor into otherwise inaccessible info. on the Valvoline site.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

I wonder if they're just playing fast-and-loose with terminology, though. I'm pretty sure I've seen/read that their formula is actually a hybrid containing some silicates. And after all, HOATs are really just a sub-class of OATs. I'm thinking that Prestone is threading a fine line so that they don't scare away GM owners.

Perhaps for many diesels, but the big boys (Caterpillar in particular seems spec-happy on all the fluids that go in their engines) still have pretty strong requirements for anti-cavitation additives that G-05 may or may not meet. That aside, my point is that there are a number of "diesel engine" coolants (aimed at the Cat, Detroit, and Cummins specs for over-the-road and off-road diesels) that are still silicate inhibited with a big dose of nitrates to prevent cavitation erosion on wet-sleeved diesel engines. No reason those shouldn't be fine in an old car that's OK with silicates.

Good sleuthing, BP. Here's another excellent article on the "Which coolant???" subject, this time by Pat Bedard with Turcotte. It's in two parts:

All this misses the simple obvious answer: Stock straight ethylene (or propylene) glycol, DI or distilled water, and additives which you add as needed!

It's nice to see that one industry isn't so paranoid of the competition and their "trade secrets" that they can actually discuss their products and the competition by name in such a manner as to provide useful information to consumers (without compromising their proprietary information).

Thanks for posting those articles. They are now also in my hard drive.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')