fewer oilings required, and less dissipation on contact with moisture inside the valve. Some synthetics have the additional advantage that they do not act as thinners for mineral-based slide greases (previously, mineral-based valve oil inserted into a valve by way of a tuning slide could carry some slide grease with it, fouling the valve). Finally, high-viscosity synthetic oils can increase valve compression and improve feel in instruments with worn valves, returning such instruments to playable condition. References Oils Petroleum based lubricants Brass instrument parts and accessories Valves