Go here: http://acsource.net/acforum/viewforum.php?f=1&sid=56f46515d37de19a161bfb3d13630d08

or here: http://www.autoacforum.com/categories.cfm?catid=2

and type in the search; you'll find many of the "old pros" use/used mineral spirits followed by a more volatile flush. On big systems I know HVAC techs who use it, followed by a dedicated, but more expensive, HVAC flush.

Here's a good one: http://store.lenzdist.com/product.php?xProd=299 and one of the most cost effective, I've found.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)