Mobil Avrex™ S Turbo 256

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Turbo engine of an aircraft

Mobil Avrex™ S Turbo 256 gas turbine lubricant is a combination of a highly stable synthetic base fluid and a unique chemical additive package.

The combination provides outstanding thermal and oxidative stability to resist deterioration and deposit formation in both the liquid and vapor phases, as well as excellent resistance to foaming. It is uniquely suited for use when extreme low temperatures restrict the use of higher viscosity engine oils.

In extensive laboratory testing and in-flight performance, Mobil Avrex S Turbo 256 exhibits excellent bulk oil stability at temperatures up to 176 degrees Celsius (350 F). The evaporation rate at these temperatures is low enough to prevent excessive loss of volume.

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Mobil Avrex S Turbo 256 is recommended for aircraft gas turbine engines in commercial and military service, particularly where start-up temperatures are below -40°C (-40°F).  The product is approved against U.S. Military Specification MIL-PRF-7808, Grade 3, and by the following engine and accessory manufacturers:

Engine and Accessory Approvals

Approved in equipment specifying 3 centistokes, MIL-PRF-7808 (latest revision) lubricants. Mobil Avrex S Turbo 256 is compatible with other synthetic gas turbine lubricants meeting MIL-PRF-7808 or MIL-PRF-23699 Specifications.  However, mixing with other products is not recommended because the blend would result in some loss of the performance characteristics of Mobil Avrex S Turbo 256.  The product is compatible with all metals used in gas turbine construction, as well as with F rubber (Viton A), H rubber (Buna N), and FVMQ rubber (fluorosilicone).


Uniquely suited for use when extreme low temperatures restrict the use of higher viscosity engine oils.

Typical properties

Avrex S Turbo 256
MIL-PRF-7808 Grade 3 Requirements
Product number 49423-7



cSt at 100°C (212°F)
3.0 min
cSt at 40°C (104°F)
11.0 min
cSt at -51°C (-60°F) after 3 hr
17,000 max
cSt at -51°C (-60°F) after 72 hr
17,000 max
Flash point, °C (°F)
224 (435)
210 (410) min
Fire point, °C (°F)
256 (493)
Pour point, °C (°F)
-60 (-75)
Specific gravity, 15/15°C (60/60°F)
TAN, mg KOH/g
0.30 max
Evaporation loss, %

6.5 hr at 204°C (400°F)

30 max
Foam, volume/collapse time

Static, ml/sec
100/60 max
Dynamic, ml/sec
100/60 max
Rubber swell, %

H Rubber, 168 hr at 70°C (158°F)
F Rubber, 72 hr at 175°C (347°F)
FS Rubber, 72 hr at 150°C (302°F)

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  • Severe operating conditions
  • Deposit control
  • Foaming resistance
  • Low temperature viscosity
  • MIL-PRF-7808, Grade 3
  • MIL-PRF-23699

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