NavList:

Hi Robert,
Having said all we have on what to use, I concur withe the chap in New Zeland, it doesn't make much difference unless you operate in extreme conditions.
Anyone of the listed substances would do and the primary consideration, since we are looking at vintage equipment with vintage materials used for gaskets and sealing, is to check first compatibility of the liquid with the materials, it doesnt make any good to have the perfect bubble just to have all the gaskets melt.
What the original manufacturers suggest obviously considered what temperatures you have at 25,000 feet into an unpressurized aircraft, so cold is not an issue. On a more actual situation, sometime we have deteriorating chambers' glass and hotter than normal temperatures, so I believe at the end it is a matter of judgment call.
Paolo
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