Just put my back axle back together, including new oil seal, o-ring and gasket. But was wondering whether I should take it apart again to put some 'gasket sealant' on there or is that just a nicety??
Or to put it another way, YES if it stops an oil leak, but only when you have it apart anyway, don't strip it down just top do it. Also, in practice, I have found that a properly fitted ring and gasket will NOT need sealant as well.