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It's come time for me to replace the dreaded lower intake manifold gasket in the Z26. I'll be doing it in the next few weeks, really just whenever I have enough spare cash to buy a torque wrench. I was talking to a friend of mine about doing this and he said if I was going to do that, I should swap out the Dexcool in the car for the regular green stuff, because, and I quote, "That **** eats up the gaskets." Is there any truth to this? I don't think so, but still, I thought I'd ask. I actually just flushed the cooling system a few months ago, and put in brand new dexcool.

Also, in an unrelated manner, I'll be replacing the exhaust system also, basically it's all  just one rusty pipe now, and was thinking about replacing the O2 sensors. Is there a set milage that you should replace them, or are they one of those things that you keep until they start throwing codes at you?

There's no proven reason to swap out the dex-cool.  Most of the gasket failures were due to a faulty (cheap) design which has been replaced.

As for the oxygen sensors, their service life is rated at 100,000 miles for the 4-wire heated sensors like your Z26 has.

The green stuff is cheaper and the Dex-Cool is better.  Just be careful with the Dex-Cool mixture as if you don't have enough water in there it tends to coagulate.  50/50 is probably best....60/40 is pushing it.  BTW, anyone know why GM switched from red Dex-Cool to orange like the Havoline stuff?

FYI, for non-heated oxygen sensors the service life is considered to be 30,000 miles.

There must just be manufacturing differences in the Dex-Cool.  Even with different year vehicles (from 96 to 04) it's always been roughly the same color.  Texaco-Havoline has always been the manufacturer for Dex-Cool.