R. Anton Rave wrote:

> I've run Dex-cool in Toyotas as old as 1986 and had a problem only
> with the very first use. The cooling system had been running green
> Zerex, so I cleaned it with oxalic acid, but apparently it didn't
> remove all the deposits because several weeks after the switch to
> Dex-cool, the overflow tank looked of pea soup. But after a second
> oxalic acid flush, the coolant stayed orange for 5 years.

I don't know about whether I would try to extend the coolant drain
period. I thought the big deal with Dex-Cool is that its "mojo"
comes from being installed in a brand new cooling system. The
corrosion inhibitors supposedly form a protective coating.

I had Dex-Cool in several cars, and none had any coolant related
problems. For one - I mixed in Dex-Cool after I'd only used green
Honda coolant in an emergency. The rad did crack at the top, but
that wasn't coolant related (it was also at 130K miles).

> I've heard that Prestone's version of Dex-cool is kinder to some
> metals than GM's/Texaco's, is, especially to soldered.

It hasn't been around that long to know. However - there is the
chance that there wasn't any reformulation - just that they got the
GM approval and license.