When it comes to spark plugs, many car owners are familiar with them. Their main function is to introduce high-voltage current into the cylinder to generate an electric spark, which ignites the combustible air-fuel mixture! Every ignition in the cylinder requires the spark plug to ignite the mixture. This places the spark plug in a high-temperature, high-pressure working environment for extended periods, making its job nothing short of "trial by fire." Over time, carbon deposits can form at the ignition point, with noticeable effects such as increased fuel consumption and difficulty starting the engine.

So, is there really nothing we can do about carbon build-up on spark plugs? After consulting with a 4S店 (authorized service center) mechanic, the expert suggested two methods: one is to replace the spark plugs, and the other is to use a fuel additive, particularly for direct injection engines, where adding a fuel additive can be very effective.

However, many online sources claim that fuel additives are a "scam" or a waste of money. Can they really clean carbon deposits? With a skeptical attitude, a Buick owner with a car that had traveled 120,000 kilometers and a Honda CR-V owner with a car that had covered over 60,000 kilometers decided to put this to the test.

Both owners inspected the condition of their spark plugs. The Buick’s spark plugs had relatively more carbon deposits.

After all, the Buick had higher mileage. In comparison, the Honda CR-V owner’s spark plugs had relatively fewer carbon deposits.

Not only did both owners check the spark plugs, but they also inspected the carbon build-up in the combustion chambers. The results were surprising—both cars had significant carbon deposits in the combustion chambers. It seemed the combustion chambers needed carbon cleaning even more than the spark plugs did.

After inspecting the carbon build-up, both owners added a 400ml bottle of Jiemo Lü (Mustard Green) cleaning fuel additive and filled their tanks with gas. They planned to drive until the tank was empty and then check if the carbon deposits had improved.

After refueling, both owners drove as they normally would, without deliberately taking highway trips. After some time, they inspected the carbon build-up again.

The cleaning results in the combustion chambers were remarkable, especially for the Honda CR-V. The bottom of the cylinder, which was originally covered in black carbon deposits, showed significant cleaning after using the fuel additive. Much of the carbon had been removed, revealing the metal’s original color. The edges also showed only a thin layer of remaining carbon deposits. It seems the cleaning power of this fuel additive is indeed impressive!