Most owners find several maintenance items that are "less" that easy access.
Is your coach on a Freightliner chassis ?
Does your filter location look like the photo below?
If your coach is on a F/L chassis , calling the free help line; with your chassis serial number; will get you your engine serial number , and possibly the filter P/N.
If they can't supply the filter number , then calling the Cat RV hotline with the engine serial number will.
Freightliner ; 1-800-385-4357
Cat RV Hotline;;1-877-777-3126 I haven't called in a few years , so hopefully they still maintain this service.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.