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Just the thing, if your tuba ever gets into the 600°F range.

I've settled on STP for tuning slides. A $3 can is a lifetime supply even if I were much younger.

One of the members from the Tromboneforum/Trombonechat has been using a jar of Dow-Corning petcock grease.

Chain saw bar oil is also good for slides that need to move but not fall out. It's not as thick as STP, more like motor oil without the odor. Also has exceptionally good film strength.
Gun oil is thinner and makes a good additive for lamp oil for use on worn pistons. Dogs used by the secret service to check a venue for bombs and guns once reacted to the tiniest odor of valve oil in the pocket of my gig bag. I wonder if that's what Al Cass has in his recipe.

I gather this stuff (`Extreme Duty') actually is not the normal gun oil that Lucas also makes.