How Much Damage Can Tiny Air Bubbles Do to Oil? Microdieseling Without a Visible Flame

When entrained air travels through a high-pressure region, damage can occur at the microscopic level.

Technical Explanation

Microdieseling involves small air or gas bubbles carried within the oil. When these bubbles enter a region where pressure rises rapidly, the bubble volume is compressed significantly and the temperature inside the bubble can rise locally due to rapid compression.

This condition can create Thermal Degradation of the oil around the bubbles, generating oxidation products or Carbonaceous Material at the microscopic level. When the event occurs repeatedly throughout machine operation, the cumulative effect can become Oil Darkening, Deposits, Filter Loading, or Varnish Precursors.

Air Ingress can originate from several points, such as a Suction Leak, Low Reservoir Level, a Return Line that causes oil to strike the surface, a Vortex, Pump Seal, or oil Air Release characteristics that are unsuitable for the system Residence Time.

It is important to distinguish Microdieseling from Cavitation and Foaming, even though these phenomena may occur together, because their Root Causes and corrective actions do not necessarily have to be the same.

Impact on Equipment

Oil Oxidation and Deposit Formation may occur faster than expected.
Pump Noise and unstable operation may result from Entrained Air.
Film Strength and lubrication may be disrupted in certain areas.
Filter Loading may increase due to Degradation Products.
The likelihood of Varnish formation may increase even when Reservoir Temperature remains within the normal range.

Recommended Approach

Start by identifying the path through which air enters the system. Check Reservoir Level, Suction Side, Pump Condition, Return Line, Deaeration Zone, and oil Residence Time. Adjusting only Antifoam or changing the oil without correcting Air Ingress may improve symptoms temporarily but will not break the cycle.

Connect the Lubricant's Air Release/Foaming data with the actual system design, and monitor Oil Color, FTIR/oxidation indicators, MPC, or Filter Condition to determine whether the corrective action reduces the degradation rate.

What Can SUTAIYO & Lubefix Do?SUTAIYO can assess whether the problem is related to Lubricant Performance, Air Ingress, or System Design/Operation by considering oil data together with Pump and system symptoms.When oil recovery or Contamination control is required, Lubefix can support Oil Filtration and Oil Conditioning. Mobil Lubricant selection is based on Air Release, Foaming, and machine requirements—not Viscosity Grade alone.

Expected Customer Outcomes• Reduce oil degradation caused by Air-related Stress.• Help the Pump and oil system operate more steadily.• Reduce Deposits and extend both Lubricant and Filter life.