If the oil thermostat is not working correctly, is it possible for the oil in the cooler to drain down into the sump, leaving the cooler empty, giving the impression there is more oil than is actually the case once the oil in the sump fills up the cooler again?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13