Diesel Fuel Supplement +Cetane Boost is an anti-gel/winterizer that is used in the cold winter months to keep fuel filters from plugging with wax and to prevent fuel gelling. This Arctic formula effectively treats all diesel fuels to keep equipment running trouble-free for maximum winter operability. Diesel Fuel Supplement is intended for use only during cold winter months when temperatures drop below 30 degree Fahrenheit. Use Diesel Kleen +Cetane Boost (in the silver bottle) for peak performance in non-winter months. If your vehicle will not start or gain power in cold temperatures, use Diesel 911 (in the red bottle) as directed on the container label.