What happens if you put 98 gasoline in a car that requires 95?

[DiWalker]

Using 98 gasoline in a car designed for 95 has no short-term effects, but long-term use can reduce the lifespan of the vehicle's ignition system, fuel injectors, and spark plugs, leading to earlier major repairs. This is the consequence of long-term mixing of different gasoline grades. The choice of gasoline grade should be based on the engine's compression ratio. Cars with a compression ratio between 8.6-9.9 should use 92 gasoline, those between 10.0-11.5 should use 95 gasoline, and those with higher compression ratios should use 98 gasoline. However, with the use of new technologies, the compression ratio alone cannot determine the appropriate gasoline grade. High compression ratio engines can be tuned to use lower-grade gasoline because other factors, such as ignition timing, turbocharging technology, and Atkinson cycle technology, also play a role. Generally, higher gasoline grades have higher octane ratings and better anti-knock properties. 98 gasoline contains 98% isooctane and 2% n-heptane, while 95 gasoline contains 95% isooctane and 5% n-heptane. Occasionally using the wrong gasoline grade is not a problem as long as you switch back to the correct grade afterward. However, long-term use of the wrong gasoline grade can have the following effects: Higher gasoline grades are not always better. The engine's compression ratio must match the gasoline grade. If a low-compression engine uses high-grade gasoline, it may reduce engine knocking but will alter the ignition timing, leading to increased carbon deposits in the cylinders. Long-term use can affect the engine's lifespan. If a high-compression engine uses low-grade gasoline, the engine is more prone to knocking, accelerating the wear and tear of engine components. Precautions: Choose gasoline with appropriate volatility based on the ambient temperature. Gasoline with good volatility makes cold starts easier and allows the engine to warm up smoothly. However, overly volatile gasoline can cause vapor lock in the fuel lines, preventing the fuel pump from functioning properly and leading to engine stalling. When refueling: Turn off the engine, avoid using phones or open flames, and maintain order while waiting in line. When selecting gasoline: Always choose reputable gas stations and the correct gasoline grade. Poor-quality gasoline can lead to increased carbon deposits in the engine. Choosing the right gasoline grade is crucial. Most vehicles have the manufacturer's recommended gasoline grade printed inside the fuel filler cap. Follow this recommendation. If the label states "Use 92 or higher," you can use either 92 or 95 gasoline, but do not mix them. If the label states "Use no less than 95," you can only use 95 or 98 gasoline, not 92. Higher gasoline grades are not always better. The engine's compression ratio must match the gasoline grade. If a low-compression engine uses high-grade gasoline, it may reduce engine knocking but will alter the ignition timing, leading to increased carbon deposits in the cylinders. Long-term use can affect the engine's lifespan. If a high-compression engine uses low-grade gasoline, the engine is more prone to knocking, accelerating the wear and tear of engine components.

[AubreyLee]

I've been driving for so many years and have tried filling cars that require 95 octane with 98 octane fuel. Honestly, there's no big issue - 98 octane fuel has better anti-knock properties, making the engine run smoother. Once on a long trip when only 98 octane was available at the gas station, I reluctantly filled up and found the throttle response became quicker, with less engine noise during acceleration. But frankly speaking, it's really not cost-effective - 98 octane costs over 1 yuan more per liter, adding up to 60+ yuan extra per tank. I specifically asked a mechanic, who said occasional use is fine, but long-term use is just burning money for nothing unless you're driving a supercar. The key is to follow the number marked on the fuel cap - if the manufacturer recommends 95, that's absolutely sufficient, no need to overcomplicate things.