Generator oil change

[Fifty4F100]

I need to change the oil in my generator before we go to the Smoky Mountains in a couple of weeks. I've tried some searches to see if I can find out a few particulars.

1.) My owners manual states in my climate I could use regular 30w oil. Does anybody use a synthetic equivalent? I don't think I've seen synthetic in 30w.

2.) I can't find any reference to what oil filter to use. Do I need to take it off and try to cross reference it at Auto Zone.

I have a Onan Marquis 5500 on my 99 Holiday Rambler.

[ArchHoagland]

I went to the local Cummins dealer and bought the filter and the oil AND the oil filter wrench to get inside where the filter is located.

It was a size wrench I couldn't find anywhere else.

[MountainAir05]

I use a 0W40 mobil one. Good for low temp and the hot 106+ out this way. Can't help you on the filter. Since I have a larger unit.