When any engine sits for a length of time there are at least 3 things to consider.
1. Humidity. Engines do circulate air in the oil system. As the engine cools from running any moisture in the air condenses and this water all be it so small rest on exposed internal components. Now these components usually will have oil on them until The engine sits for a period of time where it will eventually drain into the oil pan. After that corrosion could occur. This could cause part failure or oil contamination.
2. Unnecessary bearing wear. As stated above over time all the oil will drain into the oil pan Leaving the bearing dry. Starting the engine the next time the bearings would be metal to metal for a short period of time causing a bit of wear.
3. Corrosion/ dryness of cylinder walls for the same reason stated above. This could cause excessive piston ring wear reducing combustion or smoke out of the exhaust.
Now motor homes sit for long periods of time. The one thing I would recommend and do is put an oil additive in that “clings” itself to parts or use a synthetic/synthetic blend of oil. Now I’m not talking about the old STP type additives that looks like honey when going in. I’m talking about something like Slick 50 where there formulated to adhere to parts without gumming things up. I combat this very same issue with my aircraft engine using a synthetic blend oil and an additive called AVBlend which is a “Slick 50” type additive approved for aircraft.
i also use Marvel Mystery Oil periodically to remove any varnish in the system.
One more thing and I am taking it from the aircraft side of the house. If the engine is not used for 4-6 months the oil should be changed.
So use additives, change oil on schedule or earlier, and exercise the engine as often as you can Running up to operation temperatures before shutting down.
Sorry for the long post, but for these same reasons I lost an engine on my first plane that I bought not knowing it sat for so long without being used. The engine blew up in flight.
