Cleaners and additives. Not sure, but I don't really think that ATF is going to clean anything any better than what is in there now. Going to do it anyway, but just sayin.... What is in the tank, and is being run through the engine... Whatever fuel was left in the tank. Maybe 3 gallons or less??? About 14 to 16 gallons of fresh fuel. Enough of this, to treat about 50 gallons... And enough of this to treat about 50 gallons. Pretty sure that between all that, there isn't much left for the ATF to 'clean". Also pretty sure that all that cleaner and the gunk it is dissolving and carrying with it, wouldn't be surprising to find out that some or even most of the smoke is now coming from THAT. One of the reasons I agree with just getting a couple tanks of fuel run through.