Yep, they drink oil pretty heavily, far worse than an RGV or late TZR but your's sounds a bit much, a figure of around 200ml per 100km was recently branded about in an oil discussion thread.

NZ$35 for a litre is about right for the stuff you want to be using.
NZ$15 is a fiver (that's £5), a fiver I say! I wouldn't put £5 oil in a lawnmower.
_________________
Please do not PM me technical questions, if you can't find it on the Forum start a thread