The Non top-tier gas still has detergents in it, but not as much as top-tier. I buy most of my fuel at Hy VEE or Sam's club which is not on the list but it still has detergent in it and vehicle runs just fine. Once in a while, about 2-3 times a year I will run a tank of Shell, which is on the top tier list. I mainly go to Shell for no other reason than to go through the automatic car wash. I have seen the same tanker truck goes from station to station they will dump a load of fuel at HyVEE (not on top teir) list then down the street to unload fuel at Quik Trip (on the list) Maybe all fuel is top tier ?? Or Not. Maybe the state pump police tests for additives, I do not know. I mostly buy fuel at stations that are the most convenient, I do spend $10.00 in fuel driving all over the city looking to save a couple of cents per gallon.