I have my airplane in a hangar and try to fly it at least monthly. So why do we need to worry about corrosion more in an airplane engine than farm tractors? I have owned farm tractors that are almost 50 years old with the original engines. Oil is a lower viscosity than airplane oil so should disappear on upper engine parts and camshafts quicker. Tractor engines run in a far dirtier environment! Granted better filters but still a tough environment. Engine RPM’s are similar at full load and we pull the guts out of them during tillage activities. Some of my tractors sit for entire winters without being run, a combine may sit for 11 months without firing up. If a diesel farm tractor engine doesn’t last 5,000 or more hours it was a terrible engine, most last 8,000 to 10,000 or more. I have a 1973 dozer (original engine) with considerably more hours than that and most years it sat outside and only run in the summer months, always worked hard and definitely in the dirt. Had a 1966 gas farm tractor used for heavy tillage that sat outside it’s whole life and still had an engine that hit 5,000 hours. I bought it in 1985 and used it 20 years. It sat once for 3 years without running, probably not the best for it but put a new battery in and changed the oil - fired right up when I started it. So why are airplane engines so darn fragile regarding sitting and corrosion? Aluminum cases will contribute less rust into the engine than the cast iron and steel parts of a tractor engine. Oil changes in tractors may be once a year and more than a 100 hours between changes. Wish John Deere made an io520!