Fork oil weights

The real story...

This table is sorted by real viscosity (centiStokes), not by nominal weight.  Note that the nominal weight is ... um... not really in the same order as the real weight.

cSt is an actual standard, unlike nominal weight, which is not entirely arbitary, but more like women's clothing sizes.  Generally a size 13 will be bigger than a size 4, but you can't count on a size 9 from one designer to be the same size as a 9 from another.

The other interesting number is the Viscosity Index (VI), which is how stable the viscosity is over a wide temperature range.  Bigger numbers are better.  It doesn't just mean hot-day vs. cold day, it means begining of race vs. end. 

Brand / weight / modelnominal weightReported cSt
Reported cSt
Viscosity/ Temperature
Coefficient (VTC)
VT (cSt@40/cSt@100)
Red Line (like water, Clear)5.502.303443430.582.39
Red Line (extra light, Blue)9.804.004024030.592.45
Spectro, Golden (ultra light)10.404.403854400.582.36
RockShox (2.5w Light cartridge (Torco 5)2.510.754.003253400.632.69
Torco RFF 5510.754.003253400.632.69
Bel-Ray HVI (3 wt)311.003.852962970.652.86
Kayaba (K2-S shock)11.304.003103100.652.83
Showa Suspension Fluid SS-25
(2.5wt.  Stock Shock, OEM)
Silkolene Pro RSF (2.5wt)2.513.605.834644650.572.33
Maxima Racing Shock Fluid (light, 3wt)314.005.203783700.632.69
Torco RSF Light (purple)14.504.702882860.683.09
PJ1 Cartridge Pro For Fluid (3.5 wt)3.514.603.601340.754.06
Castrol Fork Oil (10wt)1015.004.001501790.733.75
RaceTech (Motorex) (Light US1)4.2515.204.402222260.713.45
Penske (lightweight shock fluid)15.506.304344340.592.46
Kayaba 01 (zero-One Fork)15.603.45150960.784.52
Yamaha 01 Fork oil (Kayaba)15.603.45150960.784.52
Showa Suspension Fluid SS-05
(Stock fork, OEM)
Maxima Bicycle Fork fluid (5wt)515.903.51150980.785.53
Maxima Fork oil (5 wt)515.903.51150980.784.53
Maxima Racing Fork fluid (85/150, 5 wt)515.903.51150980.784.53
Motul Fork Oil (Very Light ) ??16.003.50100950.784.57
Rockshox (52 Medium, Hydracoil) (Torco 7)716.105.052852800.693.19
Torco RFF 7716.105.052852800.693.19
Motul Shock Oil (2.5-20)16.106.204004030.612.60
showa Suspension Fluid SS-7 (5wt) (Apolo)516.443.761351190.774.37
Spectro, Golden Spectro cartridge Fork Fluid
(85/150, Very light)
Honda Pro HP Fork Oil (5wt)517.003.801401150.784.47
Pro-Circuit PC-Oil17.004.101490.764.15
Bel-Ray Fork Oil (5 wt)517.104.101461470.764.17
Kayaba G5517.703.5072720.805.06
ELF Moto Fork oil SYN (2.5)2.518.004.001211220.784.50
Motul Fork Oil, Comfort (Light 5)518.204.001241190.784.55
Motul Fork Oil, Factory Line (Light 5)518.304.201381380.774.36
Red Line (Light, Yellow)18.407.104074090.612.59
Agip Fork (2.5 wt)2.518.504.371521530.764.23
Bardahl (52 Fork Oil)19.305.102122120.743.78
Bel-Ray HVI (5wt)519.506.663453450.662.93
Torco RFF 101019.905.702602560.713.49
Motul Fork Oil (Light)??20.006.002602800.703.33
Spectro, SX "400"20.908.904004600.572.35
Maxima Racing Shock Fluid (Medium, 7wt)721.007.303493580.652.88
Spectro Fork Oil (5wt)521.604.401191140.804.91
Agip Fork (5wt)522.005.201751780.764.23
Silkolene Fork Oil (5wt)522.304.401061070.805.07
Motul Fork Oil, Factory Line (Medium, 5-10)7.522.306.202542530.723.60
Elf Moto Fork OIL SYN (5)523.304.801301290.794.85
PJ1 Fork Tuner (2.5wt)2.526.104.901110.815.33
Spectro, Golden Spectro Cartridge Fork Fluid
(125/150, Very Light) (Marzzochi)
Spectro, Golden (Very Light)26.409.904003970.632.67
Maxima Racing Fork Fluid (125/150), 7wt)726.705.361511380.804.98
Silkolene Pro RSF (5wt)526.709.463723720.652.82
PJ1 Fork Tuner (7.5wt)7.527.505.101130.815.39
Castrol Synthetic Fork Oil (5wt)528.005.701511490.804.91
Öhlins (Shock)28.709.403403400.673.05
Bel-Ray Fork Oil (7wt)729.005.201101080.825.58
Maxima Racing Shock Fluid (Heavy, 10wt)1029.009.403343360.683.09
Öhlins (High Performance)30.2510.183523520.662.97
Red Line (Medium, Red)30.4010.803693740.642.81
Agip Fork (7.5wt)7.531.006.401631650.794.84
PJ1 Fork Tuner (5wt)531.205.401060.835.78
Fox Shox (Torco RSF Medium)31.829.573003090.703.32
Torco RSF Medium (Purple)31.829.573003090.703.32
Maxima Bicycle Fork Fluid (10wt)1032.006.281511510.805.10
Maxima Fork Oil (10wt)1032.006.281511510.805.10
Spectro Fork Oil (10wt)1032.805.601111070.835.86
RaceTech (Motorex) (Medium US2)1032.907.202001920.784.57
Bel-Ray Fork Oil (10wt)1033.005.901231230.825.59
RockShox (10wt) (Torco 15)1033.008.402402470.753.93
Torco RFF 151533.008.402402470.753.93
Shell Advance Fork 5533.057.091851850.794.66
Kayaba G10S1033.205.701111110.835.82
Bel-Ray HVI (10wt)1033.5010.003063080.703.35
PJ1 Fork Tuner (10wt)1033.905.701060.835.95
Red Line D4 ATF34.007.501981970.784.53
Mobil 1 Synthetic ATF34.007.601992020.784.47
Silkolene Fork Oil (10wt)1034.907.051691690.804.95
Motul Fork Oil, Comfort (Medium 5-10)7.535.306.001151140.835.88
Bardahl (10w Fork Oil)1035.506.901581580.815.14
Showa Suspension Fluid SS8 (10wt) (Apollo)1036.477.242001670.805.04
Silkolene Pro RSF (7.5wt)7.537.0012.003223390.683.08
Shell Advance Fork 101038.977.441611610.815.24
Castrol Synthetic Fork Oil (10wt)1042.007.501501470.825.60
RockShox (15w Extra Heavy) (Torco 20)1542.8010.402502450.764.12
Torco RFF 202042.8010.402502450.764.12
Agip Fork (10wt)1045.008.301641620.825.42
Elf Moto Fork Oil SYN (10)1045.407.601351340.835.97
Spectro Fork Oil (15wt)1545.607.201191180.846.33
Repsol Moto Horquillas Fork Oil (10W20)46.008.401501610.825.48
Maxima Bicycle Fork Fluid (15wt)1546.008.481541630.825.42
Maxima Fork Oil (15wt)1546.008.481541630.825.42
Maxima Racing Fork Fluid (235/150, 15wt)1546.008.481541630.825.42
Castrol Fork Oil (15wt)1546.508.301501550.825.60
ELF Moto Fork Oil (10wt)1047.008.301531530.825.66
Spectro, Golden (light)47.2716.762353700.652.82
Kayaba G15S1547.307.201121120.856.57
Silkolene Pro RSF (10wt)1047.3613.693033030.713.46
Silkolene Fork Oil (15wt)1548.458.501531530.825.70
Bel-Ray HVI (15wt)1549.0013.902972980.723.53
Bel-Ray Fork Oil (15wt)1553.007.501031030.867.07
Red Line High Temp ATF53.9010.001721760.815.39
PJ1 Fork Tuner (15wt)1555.308.701330.846.36
Motul Fork Oil, Factory Line (Heavy, 15-20)61.0013.202242250.784.62
PJ1 Fork Tuner (20wt)2061.708.401060.867.35
Spectro Fork Oil (20wt)2065.008.901101110.867.30
Maxima Bicycle Fork Fluid (20w)2065.0012.902012040.805.04
Maxima Fork Oil (20w)2065.6012.902012020.805.09
Red Line (Heavy)66.8016.002562560.764.18
Shell Advance Fork 151567.0010.371201430.856.46
Silkolene Fork Oil (20wt)2067.708.751011010.877.74
Castrol Fork Oil (20wt)2068.0011.201501590.846.07
Repsol Moto Horquillas Fork Oil (15W30)68.0011.201501590.846.07
Agip Fork (15wt)1569.0011.501621630.836.00
Elf Moto Fork Oil (15)1572.6011.601551550.846.26
Bel-Ray Fork Oil (20wt)2073.509.501061070.877.74
Motul Fork Oil, Comfort (Heavy, 15-20)77.9010.101111120.877.71
Torco Synthetic RTF82.5014.331821820.835.76
Motorex Semi-Bath fork oil, 5W4090.9014.601691680.846.23
Silkolene Pro RSF (15wt)1592.5019.502352330.794.77
ELF Moto Fork Oil (20)2099.0014.601501530.856.78
Agip Fork (20wt)20104.0015.031551510.866.92
Silkolene Fork Oil (30wt)30105.0011.841011020.898.87
Bel-Ray Fork Oil (30wt)30105.0012.001041040.898.75
Kayaba G30S30116.1016.701561560.866.95
PJ1 Fork Tuner (30wt)30116.9015.001330.877.79
Spectro, Golden American 4 (20w50)155.0019.601461450.877.91

Credit to the source: This all came from