Tested so far, I have used it and it was perfect. I didn't have any leaks. I adapted it to a 16 lt tin and as soon as I finished filling it, I lifted the tin upright. Possibly, as mentioned in some reviews, if you leave it permanently on top and the container leans to the side, it may have some leakage. Perhaps even after some time, the rubber may loosen a bit and not have absolute sealing. Even so, I consider it a flawless product compared to the usual oil pumps where, for example, you waste 200 ml of oil that remains inside the pump to rinse it, and which, in any case, also have leaks and their placement is much worse. Also, let's not even discuss lifting the tin to empty the oil with a funnel because especially at the beginning, the oil that will spill left and right and the weight you will lift is not worth the trouble.