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Coolant Questions -- What type to buy for older GM cars?

I have a 1988 Olds 98 Regency Brougham (45K miles) and a 1988 Chevrolet Corvette (151K miles). Both vehicles are second/third owner cars and have been very well maintained. I will drive both of these cars less than 1K a year. I notice that the coolant in both is the bright green common in that era. Should I replace with the green, or would it be better for me to upgrade? What specifically should I use and why? I posted a while back about the Olds (just got the Vette) and received different opinions – some said go with Dexcool, some said Zerex (original green available from NAPA), and some said it does not matter. Can you help clarify? Thanks!

The last thing I would do is put Dexcool into it. You’d need to completely flush all of the old fluid out and then live with some of the less desirable qualities of the Dexcool.

They have coolant that is compatible with all brands and types. Read the label. This is what I bought the last time so I don’t have to worry about which is which and have a bunch of types laying around.

Do you have the owner’s manuals? I’d use whatever they recommend.

This is one of the rare circumstances where I will deviate from the owner’s manual. Rather than use DexCool and go for extended periods between coolant changes, I would buy a “universal” coolant, which can be used with almost any car and have it changed every two years. Of course, you should flush the system first to make sure all the DexCool coolant is out of the system. The label on the the “universal” coolant will tell you it can be mixed with any coolant, but I still would not mix it with DexCool.

These are both pre-dexcool so you’ll want to use the green stuff. GM had enough trouble with cars that WERE designed for dexcool so you don’t want to use it cars that aren’t. Most of the universal stuff these days is some sort of long life formulation, so even the green stuff is probably an upgrade!

If you notice the yellow colored Prestone, that’s OK too.

Just about all the new antifreezes are the HOAT type, aka universal or mixes with all types. This would be your best bet. They have the long life of Dexcool but none of the disadvantages.

Personally I’d go with the green stuff and change it once a year.

Why would you change it that often?

had a similar situation.first i flushed the dexcoolant out a few times to make sure i got most of the dexcollant out.put in the old green brand.and i will just change the collant more often . was going buy the 5 years or 150.000 miles and that was a mistake.but i caught it in time.with the advice on this form.flush the dexcollant out and use the old green coolant

Just a couple of small points:

Old-fashioned ?green? coolant seems to be mighty hard to find any more. The only place I see it is Zerex brand at NAPA.

?Personally I’d go with the green stuff and change it once a year.?

Even the green stuff has reduced silicate corrosion inhibitors today compared to yesteryear. The gelling of silicates is what forced frequent changes so every year is a little often for me, especially for the low amount of use for these vehicles.

Generally, I would not use universal-type coolants over the one recommended for the vehicle. I have not, however, personally been forced to deal with Deathcool. If you are going to go Deathcool-free, I would go with one of the universal, HOAT coolants.

I would highly recommend Evans waterless for the Corvette if you push the car hard now and then (such as taking it to a road course track). It cools better for stressed engines, but is more expensive. Since it has no water, it is easy on the components as there is nothing to corrode or freeze.

For the Olds, go with the old style ethelyne glycol coolant. Save money and don’t get the 50/50 mix stuff, and just use distilled water.