I need to service my nose gear strut and would like to know what kind of oil to use.

Pete,

 

There was a Lancair publication (SB?) that detailed servicing the strut - I don't have access to one at this time.  Check this:

 

 

I believe the recommendation for fluid was motorcycle fork oil, 20 weight.  I once tried heavier weight oil and found the castering to almost disappear in very cold weather.