I picked up the information below from the newsletter from the SW Florida Thunderbird club. CTCI's Authenticity Chairman also suggests this website for anti freeze information: www.no-rosion.com
Antifreeze manufacturers have formulated their long life products so that the inhibitor attracts, among other things, silicone compounds-the most commonly used base for gasket sealants. It also attacks lead-based products (solder, Bab-bitt), some yellow metals (cambearings, radiators) and conventional gaskets and packing materials. The warning here is to NOT use coolants with OAT– inhibitors in your antique car! You need to read the label and use only IAT (inorganic Additive Technology) Inhibited antifreeze. OAT stands for “Organic Acid Technology” based corrosion-inhibitors, and they are designed to have longer service life than that of IAT coolants; but unfortunately that feature comes with a bad side effect to older cars. One fellow decided to change antifreeze in his antique car. His regular brand was out of stock so he brought the “advanced” formula. Four weeks later he found pools of antifreeze under his car. The antifreeze had dissolved the old gaskets. It was formulated with OAT–inhibitors. Tips for finding IAT coolant are as follows: 1. Prestone says that all of their current antifreezes are OAT formulas.
2. Peak says that their Peak Antifreeze and Coolant is an IAT formula. The container is blue. It is important that it DOES NOT say “long life”. Peak Sierra brand is propylene glycol for those who prefer that. It too uses an IAT formula.
3. Zerex says that Zerex Original Green is an IAT formula. It comes in a white container. Do not use their G-05 formula in the gold jug. (This was first published in Jim Crame’s W. Michigan Buick Chapter News Letter.)
Editor note: After reading the above article, I became concerned as I had the used the Prestone antifreeze in my ’57 for the past few years. The Prestone bottle had the statement “Prestone antifreeze coolant is intended for all passenger vehicles and light trucks”. However after a trip to the local Auto Parts Store, I noticed the Peak bottle had an explanation stating “For use in Ford and Chrysler 2000 & earlier - GM 1995 & earlier - All MAKES & MODELS: 1989 AND EARLIER . I showed the above article to some auto technicians and some people behind the counter of a couple of Auto Parts stores. No one could give me an answer as to the truth in the article. I never had a problem with the Prestone; but just to be on the safe side, I drained out the Prestone antifreeze and used the Peak instead. The wording on the bottle indicated to me that maybe the Peak would be better for older cars. As always, it is your decision as to what to use in your car. Dave Tulowitzky
As Dave said I've been using Prestone for years. I'll probably change the next time I drain the radiator. John