It always amazes me that when these valves come up for discussion all of the potential problems are shown and the worst case scenarios, No one ever states how many problems there have been with leaky gaskets on the plugs, or the plugs not tightened properly, or stripped threads and pans lost from hitting objects on the road.. these Fumoto valves are build really really solid, I drove over a cement barrier once and shaved the nipple off of one and it still worked for years without a leak. After 20 years of usage I swear by them. As to oil left in after a drain,, how many shops pull the plug wait until the flow slows to a trickle and put the plug back in and refill, how much is still in the pan then???? It may take a while to feel comfortable with the valve on there but they really are reliable and very nice for changing the oil.,.