Is MMO adding sulfur in gasoline and how does that affect the gasoline. Does this make the fuel dirtier.
All fuel has some sulfur in it, this will increase it a little, but should not have an effect on burning "dirtier".
Main benefit of sulfur, of course, is that it is a great AW/EP additive for both use in the gas and fuel.
Yes, sulfur can build up on catalysts, just like phosphorous, but the other ingredients in MMO seem to keep this from happening (also known to be a great remover of lead buildup as that is why it was used in aviation applications so much). There are many testimonies of MMO being used for 200-300 thousand miles with no catalyst failures, so it must not build up due to formulation.