Hi guys. i'm changing the headstock oil and gearbox oils on my m350. I've drained them, then flushed them out with diesel and finally cleaned the bottom of the headstock with rags and kitchen roll (amaze's me how much c##p and filings do be lying in the headstock). The last time I used high quality 10w/30 tractor transmission oil just because I do have gallons of the stuff. Even though it seems to work well, with no obvious signs of wear and a nice quiet running headstock i'm just wondering if someone could advise me of the correct modern oil grade that should be used.