However, the differences between valve oils are serious, verifiable, and have a dramatic effect on how your horn will perform. There are so many trumpet oils available because there are so many businessmen who combine a little kitchen chemistry with a lot of advertising dollars to create a product. However, developing a functionally correct lubricant requires a thorough understanding of Material Science and Fluid Dynamics. Ignoring these principles has resulted in the proliferation of fundamentally poor valve oils. For example, one trumpet oil company that uses silicone oils is ignoring the hysterisis and buildup problems that plague silicones when used on sliding metal surfaces.
Some oils gunk up valves.
The primary purpose of valve oil is to provide a thin film of slippery fluid which clings to the valve and casing, thereby acting as a barrier to prevent direct metal to metal contact between these critical surfaces. To ignore either in favor of economy or naivet, is to guarantee disappointment for the musician. The most important quality in a valve oil is its ability to promote speed by reducing friction. But, the oil also causes some resistance of its own. Although you can get a rough idea about how viscous an oil is by applying some to an inclined surface and watching it run, the accurate way to measure viscosity is with capillary viscometers.