Originally Posted by 75 racer
With OBD2 cars they seen to cause EVAP codes.
A friend of mine bought one after a gas thief was active in her area. She got nothing but check engine lights, and eventually gave up on it. Of course, had I known the dealers had model-specific ones, I would have pointed her in that direction.
I don't bother with one, personally. If someone wants to go through the trouble, I'd rather replace $40 of gas than scratched paint, a bent fuel door, a broken filler hose, etc.