Are you a 50 or 100 our guy?
hours?
I start thinking about it at 50
but more often than not, by the time I actually get a round tuit, it's 75 or more
lawn and garden stuff, generators, pressure washers, etc every spring regardless of hours
but more often than not, it's summer before I get around to that too
don't over think it, BigSlim
Heat/lack of cooling air flow is far more important to air cooled engine life than chosen oil band/type
.L.T.A.