x2 I use engine oil. just a small drop is enough.Any type will due, use a small amount. This will also work on oil filters and other rubber gasket surfaces. keeps it from sticking to mounting surface making removal easier and gasket damage low.
X2, never had a problem just using diesel...diesel for the fuel filter o-ring is what I use.
:ditto: no need for extra stuff floating around in there, just dunk it in diesel before you put it on the lid, Works just fine, thats the oinly way i do mine, over 30k and about 5 different filters and no leaksI always use a drop or two of diesel, works fine.