Using castor as a after run oil is ok I think as so little is exposed to combustion.<div>The problem with running castor in four strokes is over a long period of running </div><div>it tends to gum up the valve stems and guides causing them to stick.</div><div>I prefer to run synthetics but I know some who run 2% to 5% castor.</div><div>Higher maintenance is the only result.</div><div>
</div><div>USP Castor from a pharmacy is pure and first pressing but expensive, better deal from Sig or Klotz.</div><div>
</div><div>Happy flyin', Oscar</div>