Does adding too much fuel additive affect the car?

[Hector]

Adding too much fuel additive does affect the car. Fuel additives are auxiliary fuel supplements, and long-term excessive use can increase carbon deposits in the combustion chamber, cause engine knocking or detonation, and worsen vehicle exhaust emissions. Fuel additives are directly poured into the fuel tank to clean carbon deposits, maintain the engine, improve atomization, reduce wear, and lower emissions. Adding fuel additives six times constitutes one cycle. Precautions for using fuel additives include: adding the fuel additive before refueling to ensure thorough dilution and mixing with gasoline; vehicle emissions may fail inspection tests after using fuel additives; older engines should not immediately undertake long-distance high-speed driving during fuel additive use; avoid excessive use; add one bottle of fuel additive when the tank is two-thirds or half full.

[McJanelle]

When it comes to overusing fuel additives, there's actually quite a bit to consider. Back when I worked at a repair shop, I saw many car owners pour bottle after bottle into their fuel tanks for convenience, only to end up with engines that couldn't 'breathe' properly. The principle is simple: fuel additives are primarily made of detergents, and excessive use increases the concentration too much, leading to incomplete fuel combustion. Instead of cleaning carbon deposits, it causes them to build up even thicker. What's worse, excessive metallic components like polyetheramine can corrode fuel lines and harden or crack rubber seals. Over time, the catalytic converter can also become poisoned and fail, and replacing one can cost thousands. I recommend strictly following the manual's dosage—adding 30-50 milliliters per treatment is plenty. Using more is just throwing money away and asking for trouble.

[LukasFitz]

With over a decade of auto repair experience, I've handled numerous cases of improper fuel additive usage. Overdosing is absolutely harmful – first, combustion efficiency plummets as spark plugs get coated with thick carbon deposits, and black smoke from the tailpipe becomes common. More severely, excessive chemicals in the fuel tank can wash away engine oil, causing insufficient lubrication and accelerated piston ring wear. Some vehicle models may even trigger fault codes, with the terrifying engine warning light illuminating the dashboard. The worst case I've seen involved completely ruined oxygen sensors, requiring full exhaust system disassembly for repair. Nowadays, I always advise customers to limit usage to 0.5% of fuel tank capacity, and recommend highway driving after application to promote circulation.

[AaronMarie]

Over the years of modifying cars, I've personally tested the effects of fuel additives. When the dosage exceeds the standard, the engine output immediately becomes sluggish and weak, with a soft response when stepping on the accelerator. Once, I added half a bottle extra on the track, and during straight-line acceleration, I clearly felt abnormal exhaust temperature rise. Later, after checking the information, I realized that excessive additives reduce the octane rating of gasoline, leading to increased frequency of mixture detonation. If you add excessive amounts several times in a row, the fuel injectors can also become gummed up and clogged. Now, I always bring a measuring cup when refueling—for a 65-liter tank, I only add 35 milliliters, and the effect is actually the best.