Amsoil Shock Therapy Suspension Fluid

Formulated for Fade-Free Dampening and Smooth Rebounds in High Performance Applications

Product Codes: STL STM

  • Showa
  • Kayaba
  • Bilstein
  • RydeFX Penske
  • WP
  • FOX
  • Koni
  • Harley-Davidson


AMSOIL Shock Therapy Suspension Fluids are formulated for maximum stability and high performance. High quality synthetic basestocks and high viscosity indices provide unparalleled shear stability. AMSOIL Shock Therapy Suspension Fluid controls friction and heat, reduces wear and scuffing and prevents fade more effective than conventional fluids can. AMSOIL Shock Therapy Suspension Fluid has been tested in the lab and against the competition and proven to be of the highest quality at a wide range of temperatures and applications.

Controls Dampening and Rebound

With  AMSOIL Shock Therapy Suspension Fluid, viscosity remains constant and aeration and foam are greatly reduced, significantly limiting shock fade and inconsistent dampening. AMSOIL Shock Therapy Suspension Fluid (STL & STM) is formulated for fade-free dampening and smooth rebounds in many racing and recreational applications, reducing rider fatigue and enabling the driver to ride longer and harder while keeping focused on the terrain ahead.

Reduces Friction and Wear

Constant friction in a shock body decreases suspension performance while causing scuffing and wear on the inner walls.  AMSOIL Shock Therapy Suspension Fluid contains friction modifiers to reduce frictional energy loss and heat buildup. Anti-wear agents protect against premature scuffing and wear, while maintaining proper suspension absorption.

Temperature and Performance

AMSOIL Shock Therapy Suspension Fluid features high pour and flash points, maintaining its ability to provide superior protection in both high and low temperature extremes. It is highly resistant to volatility, avoiding breakdown and resisting the buildup of sludge and deposits.

Maintains Seal Pliability

AMSOIL Shock Therapy Suspension Fluid includes seal conditioners, keeping seals soft and pliable and extending their service life.

Performance Features

  • Controls Friction and Heat
  • Reduces Wear and Scuffing
  • Effectively Prevents Fade
  • Smooth Rebounds
  • High Pour and Flash Points
  • Keeps Seals Soft and Pliable
AMSOIL STL #5 cross references to the following lubricants:
Spectro SPL Ultra Light Ohlins Front Fork #5
Race Tech Light Klotz 5W
Maxima Shock Fluid RydeFX
Silkolene Pro RSF Golden Spectro Very Light
Belray Fork 5W Bilstein Bilmst 3030
Redline Light SLP Light
PJ1 Fork Oil Showa SS05
Belray HVI 5W

AMSOIL STM #10 cross references to the following lubricants:
Spectro SK400 Shock & Fork Oil Maxima Fork Oil 10
Ohlins Front Fork Fluid #15 Spectro Fork Oil 10W
Redline Medium Belray Fork 10W
Klotz 10W Race Tech Medium
Belray HVI 10W Harley Davisdson Fork Oil Type B
Harley Davidson Fork Oil Type E Spectro SPL Very Light
Fox Racing Oil


AMSOIL Shock Therapy Suspension Fluid is recommended for front forks and shocks in snowmobiles, motocross and cruiser motorcycles, ATV’s and other racing and recreational use vehicles. Two different formulations are available: The lightweight grade (STL) is recommended, but not limited to, Showa, Kayaba, Bilstein, RydeFX, Penske, WP forks, RACETECH (US1) and Custom Axis suspension systems that demand quick rebounds under extreme hot and cold weather applications, while the medium grade (STM) can be used in Ohlin, FOX, RACETECH (US2), Koni, WP shocks and Harley-Davidson forks that recommend type “E” or “B” fork oils, as well as other applications that require more dampening and slower rebounds. Refer to the owner’s manual for individual capacities, proper disassembly and further recommendations. Owner’s manuals may refer to weights when recommending suspension oil. These weight numbers are arbitrary because no industry standard exists for classifying suspension oil. The numbers can range from 2.5 to 30, depending on the manufacturer. AMSOIL STL correlates closely to a 5 weight, while AMSOIL STM is close to a 10 weight.


AMSOIL STL and STM can be mixed together based on individual requirements and applications, and they are compatible with most other suspension fluids.

Product Availability

AMSOIL Shock Therapy Suspension Fluids are available in quarts and 5-gallon pails.





Kinematic Viscosity @ 100°C, cSt (ASTM D-445)



Kinematic Viscosity @ 40°C, cSt (ASTM D-445)



Viscosity Index (ASTM D-2270)



Pour Point, °C (ASTM D-92)



Flash Point, °C [°F]

175 [347]

202 [396]

Fire Point, °C [°F]

192 [378]

217 [423]

Four Ball Wear Test (ASTM D-4172: 40kg, 75°C, 1200 rpm, 1 hr) Scar Diameter, mm



Foam, ml (ASTM D-892) Sequence I, II, III

65/0, 60/0, 65/0

65/0, 60/0, 65/0

Blender Test (25°C, low speed, 1 min.)

2.5 mins to settle, 8% foam

2.5 mins to settle, 8% foam



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