Diesel Kleen + Cetane Boost is a total injector cleaner and performance improver that cleans injectors boosts cetane and lubricates fuel injection components. To realize the benefits of today's cleaner-burning fuels, new technology is required to maximize performance. It restores lost power and fuel economy by up to 7% and smooths rough-running engines. Diesel Kleen can be used year-round, but it is not a diesel fuel winterize or antigel. When winter temperatures drop below + 30F. use Diesel Fuel Supplement +Cetane Boost (in the white bottle) to provide maximum winter protection for your diesel engine.