Can 95 and 98 gasoline be mixed together?
4 Answers
It is not recommended to mix 95 and 98 gasoline. If the car owner has been using 95-octane gasoline, adding 98-octane gasoline once or twice will not have a significant impact, but long-term mixed use is not advisable. If the car owner intends to switch gasoline grades, it is recommended to wait until the fuel gauge light comes on before refilling with the new grade, or to directly extract the remaining gasoline and then switch to the new grade, rather than mixing them directly. The naming of 95 and 98 gasoline actually refers to the ratio of the gasoline's anti-knock performance to that of standard gasoline. For example, 95-octane gasoline contains 95% isooctane and 5% n-heptane, while 98-octane gasoline has higher anti-knock performance than 95-octane gasoline.
When I first started driving, I wondered if it was possible to mix 95 and 98 gasoline. Once when my 95 was almost empty, I added some 98 and found the car ran normally. After asking a friend at an auto repair shop, I learned that fuels can be mixed because the octane rating is just an anti-knock index—mixing them averages it out to around 96, and most engines can adapt to short-term changes. However, it's important to consider the engine's compression ratio design: some high-performance engines require high-octane fuel to prevent knocking. Mixing with lower-octane fuel may cause engine knocking, which sounds like metal clanging and can affect longevity. I recommend checking the manual for the recommended fuel grade. Mixing occasionally in emergencies isn't a big issue, but don't make it a habit. For long-term use, consistency is best. While saving money might seem good, it could lead to higher repair costs—penny wise, pound foolish.
Having driven for over 20 years, I've mixed 95 and 98 octane fuel many times. Fuel tanks contain pre-mixed blends from refineries anyway—mixing different octane ratings isn't an issue. The average might land around 96 octane, and the engine runs fine. But always check your vehicle's requirements: sports cars demand higher-octane fuel, and mixing lower grades risks knocking and accelerated piston wear. Here's a real-world example: when a gas station only had 98, I blended it with 95. The car showed no immediate issues, but performance didn't improve either. Key takeaway—don't expect cost savings or better mileage. Premium 98 is pricier, and mixing might just waste money. Always consult your manual for recommended fuel to ensure stable combustion and maximize engine longevity.
To save money, I tried mixing 95 and 98 octane fuel. 95 is cheaper, 98 is more expensive, and mixing them can slightly reduce costs, resulting in an average octane rating of around 96, allowing the vehicle to operate normally. However, the risks are high: if the car requires 98 octane, mixing in 95 can easily cause knocking, which sounds like the engine is drumming and affects performance. It's fine for short-term emergencies, like adding some during traffic jams; long-term use may lead to spark plug carbon buildup. In terms of cost, 98 is more expensive per unit, and mixing doesn't save much. It's recommended to prioritize the fuel grade recommended by the manufacturer to ensure safety and efficiency. Don't cut corners, as engine repairs will cost more.
