Some great pointers there, thanks.
I need to look up the exact engine and its manual, then. Unfortunately I haven't flown it for a land away for a while, so don't tend to look at the oil level after the flight! Next time I'll remember to do so.
I may just keep some of my own oil, good tip. I pay a wet rate so it should be 'all in' really but at least it'll mean I can still fly if there's nobody around and it's thirsty.
Thanks again!