That's fairly normal oil usage. These motors aren't like car engines, the tolerances are much much larger and can let oil past the rings etc. No matter what the manual says, the 250 motor likes the oil changed about every 1000km I've found with mine. On my next rebuild later this month, I'm thinking about just using fairly cheap oil instead of Motul, frikin' $16 every 1000km gets expensive LOL.
