its just break in oil, its full of the shit that wears as everything seats and any assembly lube used(normally molly(sp) that all ends up in your filter). maybe shitty isn't the right word, just low grade bulk oil thats only meant to be there for a short time. gotta remember, that oil filters have a bypass. once the fliter gets enough stuff in it, say metal from breaking in, it gets harder to flow oil thru it, once the pressure is high enough the oil bypasses the filter and goes back in the motor. always seemed like a good idea to me, to change it as soon as i got mine home, and did it again at 200 miles. than again at the 600. then went syn around 2500 miles.

but with that said, if all the bikes are using oil. my guess would be its either something designed wrong, like valve guides that let to much oil by, low tension oil rings that are a little to low tension in the search for every last HP. cyl plating causing the rings not to seal right, or some sort of crank case vents, either sucking oil out, or not baffled well enough.

not much you can do about any of it.