I had an amazing appliance repair man who gave me maintenance tips. He told me that because the venturi tube and its holder are two different metals, they will corrode, sieze, and eventually shear. He told me to take out all of the venturi tubes once a year, clean them, and then put some lubricant on the tube before re-installing it. The lubricant he recommended was VersaChem Anti-Seize Thread Lubricant type 13 Hi-Temp Copper Formula. I have been doing this every six months for well over 20 years. The burner we use the most is sometimes a bit dry and slightly stiff, so I do this maintenance every six months rather than every year in an abundance of caution. He said never to use too much force when unscrewing the tube, because of the risk of shearing. Maybe someone can recommend something to use if they have seized some, but not completely. May liquid wrench? I don't know.
