The Environmental Protection Agency has tested over 100 gas-saving treatments for cars, as of 2015, and none of them have proven to be significantly effective, according to About.com. Some of these products have the potential to damage engines or causes increases in exhaust emissions.
Even though the Environmental Protection Agency has evaluated many gas-saving products, long term effects of these products are still unknown. Modern vehicles have advanced emission control systems, and gas-saving products may cause problems with these systems, claims About.com. Alternate and safer ways to save on fuel include buying only the octane level fuel that is needed, using cruise control and avoiding unnecessary idling.