I went with Siikolene RSF Pro because it is a lot less expensive in Europe.Īnd don't forget to change the oil every couple of years. Redline and Silkolene have about the highest VIs available. The higher the VI, the more consistent the damping should be as the viscosity is more is consistent at differing temperatures.

Then there was the addedīonus that the theoretically 'lighter' 2.5W oil is slightly more viscous than the 'heavier' 5W at temperatures beyond 40C because it hasĪ higher VI. Mid-stroke compliance and could handle stutter bumps all the way down to 0c at which point my nutts froze. On the road the difference was immediately obvious! The forks had excellent Hence, the Silkolene should flow much better at 0c. If I recall correctly, the Widman plot showed a 30% different in oil viscosity at 0C! As you can see in that plot above, theĭifference is greatest at low temperatures. The Silkolene has more than double the VI of Amsoil (464 v 209!). So, I matched the Cst 40c with Silolene RSF pro 2.5 and It does! When I bought my Ricor Intimidators some years ago, I could not get on with the low VI Amsoil 5w recommended by | Screaming Eagle Type Extra Heavy | 60wt | 24.49 | | | | Screaming Eagle Type Heavy | 20wt | 8.60 | | | | PRODUCT | WEIGHT | 100° C | 40° C | Index | Spectro Viscosity at 40C didn't seem to match the listed SDS Viscosity Index.Ĭode: +-+-+-+-+-+ Here is some data I assembled from web sites on different fork oils.

This should give a more consistent suspension at lower temps

You can see clearly how the higher (442) viscosity Index of the Red Line Medium fork oil changes viscosity less at colder temp. I used the Widman 'Graph your oils' web page ( )to create this comparison of HD Type, Red Line Medium, Red Line HeavyĪnd the 75% RL Medium / 25% Red Line Heavy fork oils at temperatures from 0 C 32F to ~ 50C / 122F (the data on the web page goes up to 80C but isn't in the screen shot. Mentioned because some people say to use ATF in HD forks. +-+-+The VOA looks very similar to a VOA of Castrol Multi Vehicle AFT I had done several years ago as far as viscosity and additives.

Fork oil viscosity comparison chart