After having always changed my oil via the drain plug I was a little unsure of this gadget, but the 25 screws holding the belly pan on my car pushed me forward. I have to say I am a convert. The graduations on the side of the tank confirm  how much oil you gave pulled out of the engine. I allowed the oil to get just warm, not hot, and started the extraction process. It took about 30 minutes which is no worse than jacking up the car, crawling under, pulling the filter and drain plug and waiting for the oil to drain. This is much simpler and cleaner. The unit worked perfectly.