The nifty overengineered factory cap does more than put a lid on things. The torque limit rachet keeps the morons in states like Oregon from over tightening the cap so the next bloke can;t get it off. Oregon is one of those overly PC states that won;t let you pump your own gas because they are afraid you might overfill your tank. The factory cap also have aspecific venting pressure that is factored into your emmissions system. An incorrect venting cap will throw a check engine light and log a code.