Have you noticed any increases fuel consumption, higher emissions of soot, unburned fuel, engine noise and/or rough operation? Do you have problems starting your engine? Is it knocking? Or, hard start, engine stalling or refusing to start, odd behaviour, eventually making it to stop abruptly as though you’re running out of gas when climbing through steep slopes, acceleration problems, fume odor, motor sputtering, drowning when running idle, etc.?