Both of our Fs are very early, 1995 Fs, and came from the factory with ethylene glycol, aka Prestone.

A friend with a 2003 TF switched to ethylene glycol from OAT last summer, no issues to date.

Given that the very early Fs came from the factory with ethylene glycol as coolant, and there was no change to the metallurgy of the coolant system components throughout the the life of the F/TF, there is no reason that ethylene glycol cannot be used in cars that originally had OAT in the coolant system, as long as the coolant system is thoroughly flushed.

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