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. (I calculated the Viscosity Index using the Widman Calculators online ) I sent a sample of HD Type E to Blackstone for a VOA and requested the viscosity at 40 C / 100 F.
I contacted Dave at Red Line, his recommendation was to mix 75% RL Medium with 25% RL Heavy to approximate HD Type E at 40 C / 100 F.
The 'weight' the manufacturers specified sometimes didn't match the actual viscosity. Information on the web seemed to be all over the place on fork oils in general. In preparation for installing the HD screamin Eagle adjustable forks on my 2013 XL1200C I was looking at which Red Line fork oil would match HD Type E.