My fuel filter is extremely rusty so I bought a new one a couple months ago. Still haven't gotten around to putting it on but plan to do it before the weather gets too cold.
Actually, my engine light frequently comes on and goes away for "System Too Rich (Bank 1)" which I'm pretty sure relates to there being too much oxygen in the fuel. Since it just comes and goes periodically, I haven't worried too much about it but perhaps there's something I could do about that.