Aerated/foamy oil reduces lubrication effectiveness and can increase carryover.
1
Wrong oil type or mixed incompatible oils
CheckConfirm oil type against OEM spec; check maintenance records for any recent oil change or top-up with a different brand/type.
FixDrain, flush per OEM procedure, and refill with the single correct OEM-specified oil.
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2
Water contamination in oil (emulsified)
CheckOil analysis for water content; milky appearance is a strong indicator.
FixIdentify water ingress source (cooler leak, condensation from short cycling), drain and refill, repair leak.
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3
Overfilled sump
CheckSight glass level vs running spec — overfill causes churning/foaming.
FixDrain to correct level.
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4
Oil degraded/oxidized (varnish, high TAN)
CheckSend sample for oil analysis: TAN, oxidation, viscosity.
FixChange oil at OEM interval; investigate high running temperature accelerating breakdown.
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5
Return/scavenge line restriction causing turbulence
Rotary screw
CheckInspect scavenge line and orifice for restriction.
FixClear or replace restricted line.
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Safety
Lockout/tagout before opening enclosures. Verify zero energy. Bleed system pressure before opening any pneumatic connection.