RxP Fuel Additive, known as RxP Gas Kicker, works fast when added to Gasoline or Diesel Fuel to cause a more complete burn of the fuel. Carbon build-up in an engine is a result of incomplete combustion and causes high tailpipe emissions of unburned fuel. Using RxP Gas Kicker on a regular basis will de-carbonize the combustion chambers and fuel injectors and significantly reduce emissions from the tailpipe, including CO, HC, NOx, black smoke and particulates. Some customers use RxP Gas Kicker to help pass state mandated emissions test, but regular users find a more complete burn of the fuel also results in more horsepower, less engine pinging and better fuel economy. We recommend using RxP in every tankful for 3 or 4 fillups to de-carbonize the engine, then use it about every 3rd fill-up of fuel after that. This will keep the carbon from building back-up in the engine.