rec. fuel system clean. ethanol treatment to 1 tank premium. ethanol blend in fuel causes build up in fuel system(possibly fouling injectors), combustion chambers, exhaust system and causes increased wear to spark plugs. fouled injectors can cause a misfire. injectors need to spray mist to fire properly. fouled injectors lose spray and tend to squirt(firing inconsistently: misfire). result will take drive time. hope this helps.