Anti-freeze/coolant

[Joe Yakubik <75363.2524@compuserve.com>]

I might be asking a dumb question here, but is there any reason not to put plain
old green Prestone into the cooling system in Audi's?  This is the stuff in the
yellow jug.  I looked on the label and see no mention of phosphates; either the
presence of, or the lack of.  It says okay for aluminum motors.

On a related note:  is the cooling fan temp switch/sensor a 28 mm or 29 mm?  I
don't have either size socket so it may not matter.  30 is just a bit too big
and 27 is too small.  Is this inches, 1 1/8 maybe?

Related note # 2:  estimated lifespan of sensors in a '91 200:  6 years or 70k
miles.  In the past few months the multi-function temp sensor, the fan switch
sensor, the intake air temp sensor, and the o2 sensor all went bad.  Any ideas
on what's the next to go?  I'm betting it's the turbo thermo time switch.

Joe Yakubik