from my home work it seems that it acts as a cleaner in your tank so if you have a older truck it will get all the crap out of your tank and you will have to change your gas filter more often for the first year or so,, but shit it takes 5 min to change on my truck and cost only afew $,,, that is more than worth it for the savings it looks like i will get,, i also found that you will loose 1% in power, for how much power my truck has i can loose 1% for the savings....... oh and your tail pipe will smell like Burger King,