Oil Analysis takes the guesswork out of compressor maintenance by providing critical information on the oil’s physical and chemical properties. Routine oil analysis enables cost‐saving Condition‐based oil maintenance, and provides users with valuable information that can help them detect and prevent serious problems, and avoid costly repairs and downtime.


Oil-injected Rotary Screw Air Compressors are one of the harshest lubricant applications found in industry. The compressor’s forced-contamination design, elevated operating temperatures, and extreme oxidative environment create excessively harsh conditions that accelerate oil degradation and reduce the fluid’s ability to perform several key functions:

  • Lubricate Bearings & Gears
  • Remove Heat of Compression
  • Seal Rotor Clearances
  • Protect Against Corrosion
  • Prevent Foaming
  • Resist Acid & Varnish Formation
  • Deliver Maximum Service Life



Compressor fluid performance has the single greatest impact on compressor maintenance cost and reliability; and thus routine Compressor Oil Analysis should be an integral part of every compressors’ maintenance plan. Performing routine oil analysis is cheap insurance that provides compressor users with critical information that will warn of potentially catastrophic problems with the fluid, and compressor, before they occur. Oil Analysis is the backbone of Condition Based compressor maintenance and it allows compressor users to know in advance:

  • If the Fluid Needs to be Changed
  • If the Inlet Air is Contaminated
  • If Corrosion is Present
  • If Major Wear is Occurring
  • If a Different Fluid has been Added
  • If Critical Additives are becoming Depleted

Fluid Analysis is an important first step in any Reliability Centered Maintenance program, and knowing which tests are best suited for air compressor fluids is critical. Many compressor OEMs and high volume laboratories offer a one-size-fits-all oil analysis package that often includes information that is meaningless for compressor fluids. The following tests are especially useful for rotary screw air compressors and provide valuable information to help users monitor the health of their compressors’ fluid and internals, and warn of impending failures.


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Fluid Metrics’ technologies are utilized and endorsed by many of the world’s largest compressor users, and are widely recognized as the best practice in rotary screw air compressor maintenance.

Fluid Metrics, LLC

4514 Chamblee Dunwoody Rd. #252

Dunwoody , GA 30338

Phone: (770) 393-8636

Fax: (770) 393-8631

Email: info@fluidmetrics.com

Viscosity Index ASTM D2270 153
Viscosity, centistokes – cSt
@ 0° F / ‐17.8° C ASTM D445 690 cSt
@ 100° F / 37.8° C ASTM D445 26.9 cSt
@ 104° F / 40° C ASTM D445 24.9 cSt
@ 210° F / 98.9° C ASTM D445 5.2 cSt
@ 212° F / 100° C ASTM D445 5.3 cSt
Pour Point, ° F / ° C ASTM D97 ‐40 / ‐40
Flash Point, (COC) ° F / ° C ASTM D92 470 / 243
Flash Point, (PMCC) ° F / ° C ASTM D93 410 / 210
Copper Strip Corrosion, 3 hrs. @ 212° F / 100° C ASTM D130 1B
Ferrous Metal Corrosion, Rust Test
Distilled Water ASTM D665A Pass
Synthetic Sea Water ASTM D665B Pass
Foam Tendency (Sequence I, II, III) ASTM D892 0 (Nil)
Density, g/cc @ 25° C ASTM D941 0.98
Total Acid Number (TAN), mg KOH/g ASTM D664 0.18
pH Dow Method 7.9

Viscosity – cSt @ 40°C ASTM D445 44.4
Viscosity – cSt @ 100°C ASTM D445 7.3
Viscosity Index ASTM D2270 126
Pour Point – °F / °C ASTM D97 -58 / -50
Flash Point – °F / °C ASTM D92 501 / 261
Demulsibility ASTM D1401 Excellent
Foaming Sequences I, II, III ASTM D892 Nil
Specific Gravity ASTM D1298 0.89
Properties subject to change