RE: Sig castor oil separating.
Put it in the sun, then shake it up. If it disolves it's not dirt. If it does it could be water, or just some extra thick castor that doesn't want to dissolve. This happens more with high nitro fuel than low or 0% castor because castor does not dissolve with nitro. In fact the limit is 70% nitro, then even the thinnest will not dissolve.