The_Veg
D'OH!
Good to do even with horizontally-mounted filters as the oil will start flowing through them more easily and if the filter has an anti-drainback feature, it'll still hold some of what you pour in.
The difference in initial flow through new filters when primed or not was really easily observable back when I used to service medical vacuum pumps. These are the electrically-driven pumps that generate the suction used in hospitals, and their oil systems are a lot like what you'd find in an engine but without actually having an engine: they have a sump, a filter, bearings, galleries, etc., the only key difference being that the oil is pulled through the system by the vacuum generated by the pump rather than pushed through by an oil pump. The pumps use 30-weight oil (basically 'compressor oil,' e.g. Shell ND30 purchased at an auto-parts store), and an automotive-type spin-on filter. The oil both lubricates the pump and seals the vanes on the rotor. These pumps were all made in Germany and had a nice sight-glass for their oil level, very much like the sight glass used on BMW boxer engines. Listening to the sounds the pumps made after changing the filter primed or un-primed, and watching the oil level fluctuate in the sight glass was very educational. The pump was like a microcosm/teaching model of engine oil systems, since all the distractions of a combustion engine were not present.
The difference in initial flow through new filters when primed or not was really easily observable back when I used to service medical vacuum pumps. These are the electrically-driven pumps that generate the suction used in hospitals, and their oil systems are a lot like what you'd find in an engine but without actually having an engine: they have a sump, a filter, bearings, galleries, etc., the only key difference being that the oil is pulled through the system by the vacuum generated by the pump rather than pushed through by an oil pump. The pumps use 30-weight oil (basically 'compressor oil,' e.g. Shell ND30 purchased at an auto-parts store), and an automotive-type spin-on filter. The oil both lubricates the pump and seals the vanes on the rotor. These pumps were all made in Germany and had a nice sight-glass for their oil level, very much like the sight glass used on BMW boxer engines. Listening to the sounds the pumps made after changing the filter primed or un-primed, and watching the oil level fluctuate in the sight glass was very educational. The pump was like a microcosm/teaching model of engine oil systems, since all the distractions of a combustion engine were not present.
