you really shouldnt fill your tank up above that first click, however i generally do one click after that to make sure its full and the pump isnt tryin to piss me off, if you fill it right up to the brim (alot more than 2 clicks) what can happen is the fuel will run down the breather tube to the charcoal canister if you run one... and providing the canister is hooked up properly, it can cause the car to run like shit, its what destorys charcoal canisters, you'll know when its gone as you get a fuely smell thru out the car