[dataway]

What is currently the best Anti-Freeze for a 68 Pontiac? I really like the quality and longevity of the modern mixes .. but I hear some of them are a no-no for brass/copper solder joints.

[grandam1979]

I use green prestone in my 68 and in every engine that we put on test stand. The stand has a 70 Bonneville radiator on it and the car has aluminum always mixed 50/50.

[JLBIII]

Just had my original '68 4 core radiator rebuilt at a local shop. They recommended either Peak original green concentrate or 50/50 for it.

[locomotivebreath]

Peak , Prestone , even store brand - what ever is on sale and green but’d I mix it yourself and use distilled water . When you buy a 50/50 premix , you pay full price for the convenience and I’ve never been able to verify if they use distilled water - I’d bet not .

[grandam1979]

Originally Posted by locomotivebreath

Peak , Prestone , even store brand - what ever is on sale and green but’d I mix it yourself and use distilled water . When you buy a 50/50 premix , you pay full price for the convenience and I’ve never been able to verify if they use distilled water - I’d bet not .

That’s what I do also get the second gallon for a $1

[roger1]

Zerex G-05

[LM93]

You may be right about the solder brass/copper radiators. The old neon green is for those types of cooling systems, for corrosion and lubricating the water pump. Aluminum should have different additives for corrosion prevention. Definitely do not use a organic acid technology type like Dex-cool, it works in the engines it's designed for but can sludge up an open-air cooling system and dissolve gaskets. I don't know for sure if a modern mix is bad for an old system. I've had issues with my second-hand cars overheating so I'm paranoid about not having a 'perfect' cooling system. Inorganic acid tech is what the old stuff is, it's cheap, everywhere, and is meant for your old car. Then again you could have no issues with G-05, it's highly rated. Just remember, antifreeze color means nothing, it's what is on the label that matters.

[dataway]

I ask because I picked up a gallon of the G05 today, read the label ... said good for ALL cooling system metals. But my buddy there called me when I got home and said to make sure and read the label to make sure it was OK for an older car. G05 is HOAT technology I guess ... Hybrid Organic Acid Technology.

Came across this article on modern anti-freeze.

https://www.chevyhardcore.com/tech-s...eze-chemistry/

[Charlie Brengun]

I use distilled water with a quality antifreeze at a 75 / 25 ratio which is good to -14C or 7 Fahrenheit. I don't drive my car in the winter or leave it out of the garage so that mix is good enough for me.

I did this as I read distilled water is better at transferring heat than the premixed stuff (which is a 50/50 ratio).

[LM93]

Originally Posted by dataway

I ask because I picked up a gallon of the G05 today, read the label ... said good for ALL cooling system metals. But my buddy there called me when I got home and said to make sure and read the label to make sure it was OK for an older car. G05 is HOAT technology I guess ... Hybrid Organic Acid Technology.[/URL]

It may be good for all current makes and models but maybe not old ones. HOAT stuff is used in a huge range of vehicles(Ford, Mercedes), so it probably has a wide range of compatibility. I've done a bunch of internet research on antifreeze for my Firebird for when I get it going, and with aluminum rad, heater core, and heads I'm looking at G-05 as the best option. It could very well work just fine with a brazed brass rad. It's just that issues from improper antifreeze happens so slowly that retrofits haven't been around long enough to see if there are any.

Originally Posted by dataway

Came across this article on modern anti-freeze.

https://www.chevyhardcore.com/tech-s...eze-chemistry/

Eh, I would look deeper than the big-name publications for technical information like antifreeze chemistry. Sure they'll give you the basics but their market is the lowest common denominator. I'd look well past the first couple pages of search results, at places like Bobistheoilguy.com, you can find people with access to much more in-depth info there like industry bulletins from the OEMs.

BTW, yellow 'universal' antifreezes like Peak and Prestone are compatible with all makes and models like they say, they won't have a bad reaction like Dex-cool and old IAT stuff. But they're meant for emergency topping up when you don't have the right stuff available, not for filling your entire system. And you'll need to do a proper flush once you're back home.

[dataway]

Found this info on the Valvoline site concerning G05.

Looking at the test specs on the last page it seems to work well with copper and brass.

https://sharena21.springcm.com/Publi...0-ac162d889bd3

Also tracked down some info from the manufacturer/creator of G05 and they specifically recommend it for older cars.

[Tarl]

My 68 was overheating, I did a few things one of which was switching to the G-05 coolant. I went through a bunch of the classic car forums and it seems a lot of people are using it with aluminum and brass radiators in their classics. It's only been a year but no issues yet.

[Pershing]

I have kept with green IAT technology. Zerex makes Zerex Original Green which is a 5-year formula as compared to the 2 or 3 year change intervals of the old green. This Zerex meets the original GM specification GM 1899-M just like it did in the 1960's. However it is now 5 year/100,000 mile, and not the 2/3 year change intervals.

[67GTONUT]

I have been using the Zerex G-05 for years at a 75/25 ratio . Zero Issues