I use GO5 in all my cars - except the old ones with brass/copper soldered components (C2 and Pantera). While GO5/HOAT is "OK" for these applications, good old fashioned Green/IAT is preferred, due to better compatibility with the solder. Now, this no longer means Prestone, as they have changed their formula over the years. It's a little tougher to find these days! I buy my Green/IAT at tractor/farm supply stores. Zerex also offers an "Original Green" formula that they claim has some extended service properties vs traditional Green that might be beneficial. Have not tried it yet...

 

I was the Antifreeze Division Manager for a chemical company until about 25 years ago. I have stayed involved in that industry and have worked on various ASTM committees regarding antifreeze standards. The mid-1990s is when all the confusion started about the different types of new antifreeze (OAT, HOAT, etc). Basically, when it comes to antifreeze, you can put the "new" types of antifreze in old cars but you can't put the "old" type (green) antifreeze in new cars. This is due to the corrosion inhibitors blended into the ethylene glycol. (Don't use propylene glycol based antifreezes - if you can even find them). The new antifreezes have advanced corrosion inhibitors blended into them to protect the newer, more advanced engine cooling systems. These inhibitors are said to be "non-depleting, meaning that the corrosion inhibitors will never wear out (even though I was an Antifreeze Dision Manager, a Chemical Engineer, and a member of ASTM antifreeze committees, I don't completely believe that claim). They will do a better job protecting your older engine cooling systems. However, the old type of antifreeze, commonly called the "green stuff", does not have the advanced corrsion inhibitors for modern cooling systems and will damage your modern cars (such as my 2014 C7). I have a 1964 C2 and at the next coolant change, I will be putting a "new" type "extended life" coolant (OAT or HOAT) in my C2 (I've only had this car for about 6 weeks and haven't got to that work yet).
As for a little "pink" coolant in your "green" antifreeze, there is absolutely no problem with that.

 

For someone with your credentials, your brief explanation is over-simplistic...and perhaps a bit misleading. The compatibility of antifreeze additives has everything to do with the metallurgy and seal materials contained in the successive generations of cooling systems. For example, I'm pretty sure that Dex-Cool (OAT) is NOT recommended for copper/brass/solder containing systems (such as found in C1-C3 Corvettes) due to lack of protection for those metals. And GO5 is just OK in that regard. Further, I don't believe that GO5 (HOAT) is non-depleting. The recommendations is to replace that every few years. Therefore, it features a better service life vs "Green" (IAT), but not by a lot. Not meaning to debate you or question your knowledge...but it's only responsible to be more comprehensive and consultative in your recommendations given the experience that you apparently have. It would be beneficial to provide a more detailed discussion of compatibility between additive systems and materials. It helps the rest of us make a more informed decision.

 

First of all, in reply to tjpadula, if you read the bottle label, this antifreeze is designed for heavy duty truck engines. Do NOT put this in your car. That little bit won't hurt, but drain it out when you have a chance. Only use an antifreeze that is designed for automotive and light duty truck applications.

As for JohnnyRay, I'm sure that you have spent a lot of time reading up on the internet about antifreezes. There sure is a lot of various and interesting information out there. As for OAT formulations, they WILL protect your engine including parts made from copper, brass, and solder. If you want further confirmation of that, please go to the Old World Antifreeze site and the Prestone Antifreeze site. Both companies are experts in antifreezes and have been around for decades and are highly respected. They will confirm that OAT antifreezes will protect those materials along with all other cooling system components of your new or older car. Both companies have an Product Finder that show the different antifreezes that you can use in your old or new Corvette. Also note that they guarantee the newer antifreezes for up to 350,000 miles if installed and maintained properly (I would still change the antifreeze when you feel more confortable about it, personally I wouldn't go more than 100,000 miles, especially in an older car that may have not been maintained to newer car standards). They both note that the original DEX-COOL should only be used in vehicles made after 1985. Also, HOAT antifreeze seems to be on their way out since there may be some issues with that type of antifreeze in certain vehicles.

I did not go into greater depth about the chemistries and metallurgies since most Covette owners on this site want to know what to use and not the in-depth scientific background of antifreeze development.

 

Corvette owners should be making an informed choice - and appreciate the background information behind recommendations posted here to do so. Not just a selection based on a general recommendation from others. Your more recent post states that Dex-Cool should not be used in older vehicles, yet your original post didn't state that and might have led one to believe that it was recommended. You also stated generically that coolants can be mixed, yet we know that Dex-Cool (OAT) and Green (IAT) are not compatible and can form a gel if mixed. Many rely on the information posted within this forum, thus it's important to deliver a clear and concise message. I did not believe that was the case, thus my comments...

BTW - I'll stick with Green and change it regularly. After all, it's gotten my car down the road successfully for 60 years...