Entrained Air: The Overlooked Cause of Varnish and Valve Drift

Many hydraulic failures start with air in the fluid, not dirt. Entrained air speeds oxidation and causes microdieseling (bubble ignition) under pressure. The result is varnish and sticky valves that drift off target. Cold starts increase air because thick fluid bypasses and churns in returns. Reservoir design and dwell time decide how fast bubbles can escape. Choose fluids with quick air release and controlled foaming for stable control. Shear-stable viscosity modifiers keep clearances sealed in both warm and cold. Anti-wear additives need temperature to react, so allow gentle warm-up before load. Water also raises cavitation risk and should be checked during service. Find a fluid with these traits and proven balance in HVLP46.