Add it to the oil Before changing it. Only let it idle, i pour it into a warm engine. Let it idle a while then Change the oil. Much like Any flush I Do Not drive with it in the oil.
mechanics around here swear by it. usually as a carb cleaner for them. they have different methods. basically use in carb in runnin car, and some pour half bottle in carb and let sit for hours to overnight. yes it can smoke!!