Is the correct sequence for adding fuel additive to fill up the tank first or add the additive first?

[OCorey]

The correct sequence for adding fuel additive is to add the additive first and then fill up the tank. Fuel additive, commonly known as fuel system cleaner or gasoline additive, serves the following functions: 1. Remove carbon deposits; 2. Improve atomization; 3. Protect the engine; 4. Reduce engine wear; 5. Eliminate black smoke and lower emissions. Precautions for using fuel additives include: 1. Pay attention to purchasing branded fuel additives and avoid randomly using those recommended by repair shops; 2. New cars should not rush to use fuel additives; 3. Do not rely solely on fuel additives to clean engine carbon deposits—driving habits should also be taken into consideration.