Our multi-functional fuel system cleaner for automobiles is carefully formulated with methanol and diethylene glycol monobutyl ether. Designed specifically for effectively removing carbon deposits from engines and restoring engine power. The usage method is extremely convenient: Before refueling， please add this product to the fuel tank and then fill it up. Vehicles that have not been cleaned for a long time may emit black smoke during the initial cleaning process. This is the result of a large amount of carbon deposits being removed. Afterwards， during the normal cleaning stage， the black smoke will decrease and eventually disappear. It is recommended to clean and maintain the vehicle every approximately 5，000 kilometers. For vehicles that have not been cleaned for a long time， it is recommended to use this product twice in a row. Do not clean under the following circumstances: the catalytic converter is overheated， charred or contaminated with lead， the catalytic converter is severely clogged， or the engine is burning oil. Only after these problems are solved can the vehicle be used. And it helps to reduce vehicle emissions， making driving more environmentally friendly.