Problem with anything but a genuine Onan OIL filter is the length.
These aftermarket short filters will spin on and work, but...
All aftermarket filters for the Onan I've seen/used is the length is to short to hang below and 'seal' the serrated rubber shield/gasket that keeps in the cooling airflow for the genny/engine. And keeps out road debris/dirt.
For those that haven't seen this extra gasket on the Onan chassis oil filter opening, its not the gasket in the base of the oil filter.Its another gasket that semi-seals the top of the oil filter canister.And it needs the filter long enough to hang down thru this seal/gasket.
This added length of a genuine Onan oil filter also makes it easy to grab the filter and spin it off/on no problem. No filter 'nut' is needed if you use the Onan filter. Tighten by hand is all I ever use on my filters(on any motor). Never have leaks or problems, ever. Feel it out, feel when the filter seats and the thick rubber gasket(or o-ring) starts too compress, then just another 1/4 to 1/2 turn will 'feel' tight and fully seated. Do not over torque a filter with a filter wrench. Filter wrenches are for taking off stubborn filters.
Never torque down an oil filter, always only hand tighten nice and 'snug'after cleaning the mating surface on block and oiling the gasket well. And use your eyes when cleaning off the blocks oil filter mating surface. Make sure the old gasket is not still stuck to engine, 2 gaskets is not ideal and a major cause of oil filter leaks...
I'm a firm believer in filling the filters full of oil before installing it to avoid cumulative extra wear from a dry start every oil change.
jmo