All I'll say is that when I *fill* my tank, the car smells of gas.. after 5-10 miles it's gone. I just figure when it's super full some gas sloshes down the vent and you can smell it. I don't have a charcoal canister or anything, just an open-ended hose, so I was always surprised it didn't smell all the time (it's just an open hose to a tank of gas after all!)