The appearance of brownish-red deposits on spark plug surfaces cannot be simply categorized as ordinary carbon buildup; it is more likely MMT contamination.
MMT contamination is essentially the subsequent effect of residual gasoline additives. MMT stands for methylcyclopentadiene trihydroxymanganese compound. It is well known that higher gasoline octane ratings generally correlate with better anti-knock performance. Adding MMT to fuel can increase the octane rating at a relatively low cost, thus aiding in the blending of high-octane unleaded gasoline. However, this method of addition has been controversial within the industry.
From the perspective of the spark plug's operating environment, after the high-temperature combustion of MMT in the engine, its core component-manganese-does not disappear but transforms into various manganese oxides, primarily manganese trioxide and other complex oxides. These substances adhere and deposit in the form of solid particles, ultimately forming a noticeable reddish-brown or rust-colored coating on the spark plug surface.
It is crucial to understand that the damage MMT contamination inflicts on spark plug performance is not as simple as that caused by ordinary carbon buildup. For spark plug systems that emphasize ignition stability, durability, and high performance, these deposits directly affect normal operation.
Harm 1: Damage to Insulation Performance, Causing High-Voltage Leakage
The crucial role of the spark plug ceramic insulator is to ensure that tens of thousands of volts of high-voltage energy are concentrated on the electrode gap for stable ignition. However, mixed deposits such as manganese trioxide and manganese tetroxide possess certain semiconductor properties. When they accumulate to a certain extent on the ceramic surface, it's equivalent to forming an additional conductive path on the originally insulating surface. This can cause high-voltage electricity to leak along this "bypass," leading to a decrease in the energy actually used for ignition.
Harm 2: Increased Ignition Voltage, Increased Load on the Ignition System
When these deposits cover the electrode surface, they alter the physical conditions and electric field distribution near the electrode gap. To successfully break down the contaminated gap and form a spark, the ignition coil must output a higher voltage. Prolonged exposure to this high load makes the ignition coil more prone to overheating, accelerated aging, and even premature damage.
Hazard 3: Misfire under Specific Operating Conditions, Leading to Power Loss
As engine speed and load increase, cylinder temperature rises accordingly, potentially enhancing the conductivity of manganese deposits. This risk of misfire increases significantly, especially under high load and rapid acceleration conditions requiring strong ignition energy. If the air-fuel mixture fails to burn properly, the vehicle will experience power interruption, sluggish acceleration, and jerking, directly explaining why many customers feel their car lacks power.
Once spark plug contamination (MMT) is confirmed, it's crucial to understand that this type of deposit is irreversible chemical and cannot be safely and thoroughly removed through conventional cleaning methods. The only truly reliable solution is to replace the spark plugs.
Of course, MMT contamination is not entirely unpreventable. Proper management during use and maintenance can effectively reduce its probability.
First, prioritize source control and choose reliable fuel.
Refuel at reputable gas stations with well-managed operations and stable fuel sources whenever possible. These channels typically have stricter control over the quality and proportion of additives, reducing the risk of excessive MMT exposure at the source.
Second, establish a proactive inspection habit to detect problems early.
It is recommended to check the spark plugs every 15,000 to 20,000 kilometers. Early identification and treatment not only prevent further degradation of spark plug performance but also help reduce cascading damage to the ignition coil and the entire ignition system.
