Kira, the FV web site claims that their gadget is so good that it actually received OEM part status from a number of Japanese manufacturers, including Mazda. I used a Fram Sure-Drain on my 89 Accord for years, with a nylon washer, and it didn't leak. I put a FV on the Mazda at the first oil change, 2,500 miles ago. Since the plastic splash shield on this car has a removable hatch to access the oil drain and filter I guess I won't know if it's leaked until my next OC. The blue washer it comes with is fiber so, much like a nylon washer, you can't muscle it down as hard as you would with a metal washer. I think that's a good thing. I only use plastic washers. I've had plenty of aluminum and copper washers ooze or drip, but the plastic washers work for me every time, on multiple cars, for the past thirty years.