I run my tractors at the governor all day and don't have that issue. My teenage son runs his 1976 240 at 80+ every time he gets on the interstate and doesn't have this oil burning issue either and his blow by is much worse than this one.
I think its related to the oil separation unit. My guess is that the oil cant flow through it back to the pan at those RPMS so it goes directly into the intake.
I am going to take it apart and try to clean it.

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1985 300 TD 448K
1984 300 TD 278K

1983 240D euro 240k
1994 f-250 idi turbo 330K
1986 f-350 IDI
1987 F-350 IDI

1985 JD 1050 4wd
1965 IH 3660