An Environmentally Acceptable Lubricant for use in stern tubes /
Friendly to the Seas


From 2006, KEMEL began to supply own biodegradable lubricant “ST-77” and special seal designed for it. In 2014, the lubricant was changed to “ST-83A” to meet 2013 VGP of US EPA.
Now, KEMEL has developed the third generation lubricant “BIO ST-100” for the purpose of further improvement of bearing lubricating performance.
“ST-83A” will be switched to “BIO ST-100” in sequence from now on.


Base Fluid

Poly glycol, a type of poly glycol, is well known as non-toxic material.
It is generally applied in cosmetics and medicines.

No Sheen / No Sludge

BIO ST-100 is water soluble and forms no sheen or discoloration to the water. Also produces no sludge or emulsion under water surface.

High Seawater Tolerance

BIO ST-100 provides excellent lubrication and corrosion prevention even when the seawater content is 10%, because BIO ST-100 dose not occur hydrolysis like ester based EAL.

Bearing Lurication

BIO ST-100 is classified VG100 viscosity grade, and has higher dynamic viscosity than mineral oils and ester based EALs of VG100. BIO ST-100 gives thicker oil film than the other VG100 oils.
(Note)VG: Viscosity Grade

KEMEL BIO ST-100 Typical Mineral System Oil (VG100)
Dynamic viscosity@40℃ 122mPa・s 93mPa・s

2013 VGP of US EPA

BIO ST-100 meets the EAL (Environmentally Acceptable Lubricant) specification in 2013 VGP of US EPA.

  • BiodegradableOECD 301B test method found BIO ST-100 readily biodegradable.
  • Non-ToxicBIO ST-100 has been classified as harmless to aquatic lives under OECD 201, 202 and 203 tests.
  • Non-Bioaccumulative BIOST-100 is not bioaccumulative to aquatic lives because it is water soluble.

Improvements of BIO ST-100 from ST-83A

  • Higher ViscosityHigher performance of oil film formation
  • Lower Pour pointBetter fluidity at low temperature
  • Higher Flush pointFire-retardant (flash point > 250 C)

Important Notice

  1. For stern tube seals, KEMEL special seals of advanced fluoric rubbers (FKM for PAG Bio/FEPM) should be applied.
  2. No chemical reaction occurs even if KEMEL BIO ST-100 is mixed with ST-83A. However, to conduct used lubricant analysis properly, please drain out ST-83A fully before filling the stern tube with Bio ST-100. No special flushing is necessary.
  3. LO In case of cleaning the inside of stern tube, pipes and tanks by flushing, BIO ST-100 (or ST-83A) or turbine oil should be used as flushing oil.
  4. Piping design should be consulted with KEMEL. KEMEL BIO ST-100 may absorb water from moisture in the air because KEMEL BIO ST-100 is water soluble.
  5. Epoxy paint should not be used for tank inside. Zinc-rich primer or non-coating is recommended.

Environmentally Acceptable Lubricant For Stern Tubes / Marine Hydraulic Systems KEMEL BIO ST-100


Base fluid: Poly glycol

■Physical and Chemical Properties

(1)Typical Properties
Appearance Pale yellow liquid
Viscosity at 40℃ 106mm2/s
Viscosity Index 126
Density at 15℃ 1.15g/cm3
Pour Point -38℃
Flash Point 280℃(COC)
Solubility Soluble in Water
(2)Environmental Properties
Property Test Method Typical Result
Biodegradability OECD 301B > 60%
Toxicity OECD 201 (alge)
OECD 202 (daphnia)
OECD 203 (fish)
> 100mg/L
Bioaccumulation OECD 107, 117 Log Pow < 3
Sheen or sludge
Visual No sheen / No sludge
(3)Functional Properties
Property Test Method Typical Result
Rust protection (steel) ASTM D665
(Sea water)
No rust
Corrosion protection (copper) ASTM D130 1a
Foam suppression ASTM D892 90/0 @24℃
Oxidation stability ASTM D2893 Viscosity Change: 6% @40℃