Sorry for the really stupid question...I am looking to remove the OMP and run pre-mix only - I have been running a 400:1 mix in the tank (give or take) up until now, but I have noticed that the oil level hasn't really dropped in the sump, so I assume the OMP isn't working??? I am not sure how much should it use, but I'd guess at more than it has...

Once I have removed the OMP, what pre-mix ratio should I use?