LUBRICATION GUIDE
Hydraulic Oil Change Interval: Change on Condition, Not the Calendar
By the PCG Technical Desk · Updated 27 September 2026
Quick answer: Change hydraulic oil when analysis shows it has degraded or become contaminated, not on a fixed calendar. Sample critical systems every 3–6 months and general systems every 6–12 months. Change or clean up the oil when viscosity moves out of range, acidity rises, water or particle counts exceed your targets, or additives are depleted.
Why fixed intervals waste money
A clean, cool system can run the same oil for years, while a hot, dusty one may degrade it in months. A fixed interval either throws away good oil or leaves bad oil in the machine.
What to test
- Viscosity @ 40 °C: a movement of more than about 10% from new-oil value needs investigating.
- Acid number (TAN): a rising trend indicates oxidation.
- Water: keep it as low as practical. Hydraulic systems generally aim for a few hundred ppm or less. Free water is always a problem.
- Particle count (ISO 4406): compare against the target for your most sensitive component (see oil analysis limits).
- Additive elements / wear metals: show depletion and component wear.
Extend oil life
- Control temperature: clean coolers and check fans.
- Fit desiccant breathers and keep tanks sealed.
- Filter new oil on fill, since new oil is not always clean.
- Never top up with a different oil type.
Our oil analysis service helps set intervals for your plant. Recommended oils: Servosystem 68, Servosystem HLP.
Outside Karnataka? The technical information on this page applies anywhere in India. PCG Business Solutions supplies SERVO in seven Karnataka districts. If you are in another state, send us your requirement and we will point you to IndianOil's authorised channel for your area, or answer any technical question about the grade.
