Don't over tighten the bolt through the oil filter, I have new filters and O rings here in Rugby... bolt only needs tightening to 14ftlb, any more and you can mishape the cannister and it'll leak oil for ever more.
If it's have some dubious oil through it it, then you will need to change theoil 2 or 3 times as you only ever ( at best ) change 2/3rds of the oil in each change..
Once it's started flaring into top, then there's no real coming back, the damage has been done.
Would synthetic oil be classed as dubious?
I think once the lockdown is eased I'm just going to put it on ebay with an honest description