Unfortunately the EPA accepts > 50 chemicals as detergents for gasoline and there are no public tests about how much of what cleans how much.
Some detergents actually create new deposits while cleaning other deposits. Sometimes it is better to use [alternate between] two different brands if they are infact different!
"Engine dynamometer tests were conducted to evaluate the effect of detergent additives and gasoline components on combustion chamber deposits (CCD). Additives with polyether amine (PEA) and with polyolefin amine (POA) chemicals were used. Our results show that some kinds of additives and aromatics in gasoline increase CCD formation. Deterent polyolefin detergents show different tendency of CCD formation.
The amount of CCD showed good relationship with the unwashed gum level of the gasoline. In general, smaller dosages produce less CCD. This means that detergents which have good IVD and PFID effectiveness at smaller dosage are better with regard to CCD."
http://www.epa.gov/OMS/regs/fu...s.htm
"Gasoline detergents are commonly employed in gasolines for the purposes of maintaining fuel system cleanliness, absorbing traces of moisture, and resisting rust and corrosion. It is desirable that such detergents be ashless--that is, contain no metal salts and burn cleanly in the combustion chamber. It is further desirable that they contain no elements such as phosphorus which could be detrimental to the performance of a catalytic converter or other emission control device. Gasoline detergents of choice in our invention are the fatty amines and the ethoxylated and propoxylated derivatives thereof, as well as fatty diamines such as tallow propylenediamine. The reaction of a fatty acid having from about ten to about twenty carbon atoms and mixtures thereof with ethylene diamine or derivatives thereof such as N-hydroxyethyl ethylenediamine gives rise to cyclic amines called imidazolines. These fatty imidazolines are very useful as gasoline detergents. Polymeric amines and derivatives thereof such as the polybuteneamines and polybuteneamine polyethers have also proved efficacious as gasoline detergents and are claimed to offer some advantages over conventional amines, especially in the area of intake valve cleanliness. The amines, diamines, fatty imidazolines, and polymeric amines are all useful as the gasoline detergent components of our invention. In combination with these amines, carboxylic acids may be used, as is well known in the art, said carboxylic acids having from three to forty carbon atoms. Among preferred carboxylic acids to be used in combination with the amine detergents are the 2,2-dimethylalkanoic acids having from about five to about thirteen carbon atoms, oleic acid, and the dimerized acid of linoleic acid. "