|Style over substance
Gas-saving magnets are devices installed on the fuel line line of automobiles that purport to reduce fuel consumption by using a "Neodymium Rare Earth Magnet" for "splitting the hydrocarbon chain into smaller components with their subsequent ionization, which in turn leads to more complete combustion of gasoline or diesel fuel". In other words, pure automotive woo.
Supposedly, these ultra-powerful magnets allow the "hydrocarbon clusters" to more easily vaporize. Though anyone with basically a high-school education in chemistry and physics should know that this is utter nonsense, they are nonetheless sold in the US for around $30 and claim to improve fuel-efficiency by 20%, so you can't afford not to buy one.
In 2004 the FTC brought charges against one magnet manufacturer, FuelMax, which eventually settled for 4.2 million US smackaroons, though the devices are now available to the general public through a totally different company, FuelMag.