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Pour oil into the valve via the tuning slide?

I seem to recall that some deplore that, but the first several how-tos I pulled up online tell me to do it. Seemed to help a lot with a sluggish valve.

Some of us pour it down the leadpipe. After every time we play, using Lamp Oil, because its cheap. I have started doing this after reading blokes posts. My method is to pour down the leadpipe, wiggle the rotary valves, then next time you play pull the tuning slide out and drain before you play.

You could also try pulling the second valve slide and pouring the valve oil down into the second valve. Just try not to get it on the slides because it might wash the grease off into the valves.

After doing this I find the valves never bind and cleaning the leadpipe with a snake/trombone type cleaner got the crud out better, mainly because it was less likely to stick to the leadpipe.