I didn't catch this at first, but if you have greenish oil you are probably using Coolpoweer which has no castor. That is why you have little smoke. The FX should have some castor oil in the mix. Yes for the first few tanks the oil should have been almost black. This is the aluminum wearing off the piston. Once broken in (like several gallons) the oil may be clear (but maybe not due to castor varnish in the muffler), but till then slightly grey is normal.