Okay, so I just read through 200 of the 420 threads on Sump filters trying to see if anyone addressed this question and don't see a discussion on it. "Why doesn't the owner's manual for my '81 SH mention anything about the sump filter needing to be checked/replaced periodically?" All it addresses is the regular oil drain plugs and filter. If the sump filter should be checked/cleaned/replaced periodically I would think it would be included in the maintenance schedule in the manual.
If it weren't for this forum I wouldn't even know there was a sump filter.
If it weren't for this forum I wouldn't even know there was a sump filter.