I'd say they're pretty efficient on the carbon levels, it is a BMW. But I just couldn't see one being used for offroad, haha. We have an '85 Bronco right now.. woo. V6 carb powered. Woo. It puts out it's fair share of "gasses" >.>
I luv the Bronco, classic offroad, i'd swap one for an X5 anyday...