Hi PF, I really didn't know where to ask the following question so redirect the thread if necessary. I'd like to know why I can't really "close" cooking oil bottle caps. I can screw the oil bottle caps but when it's almost totally screwed, suddenly it's like it unscrew and I have to screw it again and stop just before it unscrew. It happens with any brand of cooking oils so there's a good reason to use this kind of bottle caps. Until now I don't really have any idea about the reason it is so. If you know it feel free to explain it to me. Thank you.