Is it okay to use vegetable oil instead of valve on a tuba?

Vegetable oils are not effective at lubricating the valves of a tuba. They are too viscous, and can actually cause the valves to stick. In addition, vegetable oils can gum up the valves and cause them to become permanently damaged.

You should use a specifically formulated tuba valve oil that has been designed for that purpose. Valve oils are made from a variety of different ingredients, including mineral oil, synthetic oils, and essential oils. They are designed to provide the right level of lubrication for tuba valves, and they will not damage the valves over time.