mt 46AX spit dark oil for a couple of galons when it was new, towards the end of the last gallon it began to clean up a bit, another thing you wil notice is the new plug will foul after the first few tanks, this is normal its because of the micro metal fragments that get into the plug durring the break in process,tend to break the plugs down,after the #3 plug that comes with it fouled, I switched to a #8 its been in there ever since, as long as your running a little rich your good to go.