In industrial plants running hydraulic, turbine, gear, or lube oil systems, oil topup is one of the most routine — and most overlooked — maintenance activities. A poorly executed topup can introduce dirt, water, and the wrong oil grade into your system, undoing months of careful contamination control in minutes. Following correct oil topup practices protects component life, maintains ISO cleanliness targets, and reduces unplanned downtime across steel, cement, plastic, and oil & gas operations. Here are four essential oil topup practices every plant maintenance team should follow.
1. Always Use the Same Grade of Oil
Mixing oil grades — even within the same base oil type — can alter viscosity, additive balance, and chemical stability, leading to sludge formation and reduced lubrication performance. Always top up with the exact same grade of hydraulic, turbine, gear, or lube oil already in the system. If a change of oil grade is unavoidable, the system must be flushed thoroughly before introducing the new oil. Flushing removes residual additives and contaminants from the old oil, preventing chemical reactions that can damage seals, valves, and bearings. A proper flush also ensures the new oil performs to its full specification from day one.
2. Use Clean Filter Caps and a Clean Funnel for Oil Transfer
Most contamination doesn't come from the oil itself — it comes from the transfer process. Dust, metal shavings, and fibers from rags or unclean containers are common culprits behind particle contamination during topup.
Best practices include:
•Always wipe down filler caps and surrounding areas before opening
•Use a dedicated, clean funnel exclusively for oil transfer — never share funnels across different oil types
•Store funnels and transfer equipment in sealed, dust-free containers between uses
•Inspect oil containers for seal integrity before opening
These small steps significantly reduce the risk of solid particle ingress, which is one of the leading causes of premature wear in hydraulic pumps, valves, and turbine bearings.
3. Shut Down and Depressurise the System Before Topup (Where Possible)
Topping up a pressurised, running system increases the risk of air ingress, oil spray, and operator safety hazards. Wherever operationally
feasible, shut down the equipment and allow the system to depressurise fully before opening any filler points.
This practice:
•Minimizes air entrainment, which can cause cavitation and oxidation.
•Reduces the chance of oil contamination from atmospheric exposure during active operation.
•Improves operator safety by eliminating pressurised oil spray risks
•Allows the system to reach a stable level reading for accurate topup
For systems that cannot be shut down, ensure topup is performed only by trained personnel
using appropriate PPE and equipment rated for live conditions.
4. Verify Oil Levels and Fill Within the Recommended Range
Before adding oil, always check the reservoir or sight glass level indicator. Oil should be maintained between the marked maximum and minimum levels — never below the minimum, which risks pump cavitation and overheating, and never above the maximum, which can cause foaming, overheating, and seal leakage. After topup, allow the system to run briefly and re-check the level once oil has circulated and air has settled, as initial readings can be misleading during static conditions.
Protect Your Investment with Professional Oil Filtration
Even with the best topup practices, hydraulic, turbine, gear, and lube oil systems accumulate moisture, particulate, and oxidation byproducts over time. Regular oil analysis combined with offline filtration is essential to maintain ISO cleanliness targets and extend oil and component life. Liasotech Pvt Ltd designs and manufactures Oil Filtration Machines and Vacuum Dehydration Systems for hydraulic, turbine, gear, and lube oil applications — trusted by plants across the steel, cement, plastic, and oil & gas sectors. Our systems help you remove water contamination, reduce particle counts, and keep your oil performing like new.
Contact Liasotech today to discuss a customised filtration solution for your plant.