sewing machine oil is pretty lightweight.
Others have over time suggested 30w Non Detergent.
IF the hub has been sitting for a long time... decades even.
I have flushed it out to dissolve the "varnish" (monitor the color of what flushes out)
Then 30 w.
After repacking the outboard bearings
Oh, if it has an earlier metal flip lid port, park the bike with the oil port up.
The plastic ports sealed better, even they leak some.
The seal on the metal lids are most likely dead.