"The FTC's complaint alleges that the defendants did not possess and rely on reasonable substantiation for the following claims in the infomercial, on the Web site and in brochures that zMax:
increases gas mileage;
increases gas mileage by a minimum of 10%
reduces engine wear;
reduces or eliminates engine wear at startup;
reduces engine corrosion;
extends engine life; and
reduces emissions.
...zMax produced more than twice as much bearing corrosion than motor oil alone"
http://www.ftc.gov/opa/2001/02/zmax1.shtm
"According to the FTC, the enhanced performance benefits zMax claims its products provide are totally unsubstantiated, and in the same tests cited to support performance claims, motor oil treated with zMax actually produced more than twice as much bearing corrosion than motor oil by itself"
http://www.syntheticsgroup.com/after...additives.html
"tests cited to support performance claims actually demonstrated that motor oil treated with zMax produced more than twice as much bearing corrosion than motor oil alone, and that the three different products - an engine additive, a fuel line additive and a transmission additive - were all actually mineral oil tinted with food colouring"
http://www.carbibles.com/additives.html