Mixing 87 and 93 gasoline is not inherently dangerous for most engines, and the vehicle won’t suddenly break down from a blend. The resulting octane will land somewhere between the two grades, depending on how much of each you pour, and whether that level meets your car’s requirements.
In many regions, drivers blend fuels to balance availability, price, and performance. This article explains how octane works, how blends behave in practice, and when it’s reasonable—or inadvisable—to mix 87 with 93. It also covers what modern engines do if the octane level isn’t exactly what the manufacturer calls for.
How octane works and why it matters
Octane is a measure of a fuel’s resistance to knocking (pre-detonation) in an engine. High-compression and turbocharged engines are more sensitive to octane, while engines designed for regular-grade fuel may not benefit from higher octane. When the octane is too low for the engine’s demands, knocking can occur, which can reduce power, efficiency, and, over time, potentially harm the engine. Modern cars with knock sensors can adjust timing to prevent severe knocking, but this can come at the cost of performance and fuel economy.
Before blending, here are key considerations to keep in mind when you encounter different octane grades at the pump.
- The octane rating of a blend is roughly a volume-weighted average of the components, so equal parts 87 and 93 will land near 90 AKI. Additives and ethanol content can slightly shift the final number.
- Whether a mixed fuel actually helps or harms depends on your vehicle’s octane requirement. If the engine is designed for premium (often labeled 91–93 AKI in the U.S. or higher), a lower-octane blend may reduce performance or trigger knock under load.
- Gasoline blends differ in ethanol content (such as E10). Differences in ethanol can affect driveability and fuel-system behavior, especially in older or specialized engines.
- For engines with knock sensors, the engine may retime or adjust timing to prevent knocking when octane is lower than ideal, which can reduce horsepower and efficiency.
Conclusion: Mixing 87 and 93 won’t harm a typical modern engine, but the resulting performance depends on whether your car actually needs the higher octane. If your manual calls for premium, a lower-octane blend can compromise power and efficiency under certain driving conditions.
When blending is likely acceptable or not
Understanding when it’s reasonable to blend—and when to avoid it—helps drivers decide how to fuel up in daily life.
- Acceptable when your vehicle is designed to run on regular-grade fuel and you’re blending to save money without pushing the engine into high-load conditions.
- Not advisable for engines that require premium or have high compression, forced induction, or performance-totential that relies on consistent octane levels.
- Less beneficial in hot climates or when towing, since higher load and heat increase the risk of knock if octane drops.
- Not a long-term fuel strategy: if you mix to meet a temporary shortage, refill with the appropriate grade as soon as possible to restore the engine's designed octane level.
- Be mindful of automatic adjustments: modern cars may compensate, but fuel economy and power can still suffer if the blend is consistently below what the manufacturer recommends.
Conclusion: Blending can be fine in a pinch for many engines, but it is not a universal solution. When in doubt, follow the vehicle’s octane recommendations found in the owner’s manual and on the fuel-filler door sticker.
Practical guidance for drivers
To avoid surprises and keep performance consistent, consider these practical steps.
- Check the owner’s manual or door-jamb sticker to confirm the recommended octane for your vehicle. Some engines are tolerant of a wide range, while others require premium.
- If you decide to blend, estimate the resulting octane. A rough rule of thumb is a volume-weighted average; equal parts 87 and 93 yield around 90 AKI, but additives can shift this slightly.
- Monitor how the engine behaves after fueling. Listen for pinging or knocking sounds, especially under acceleration or uphill climbs. If you notice issues, refuel with the recommended grade as soon as possible.
- Avoid routinely mixing to compensate for running low on the right grade; repeatedly using a sub-recommended octane can reduce performance and efficiency over time.
- Note ethanol content differences. If one fuel has a different ethanol percentage than the other, the blend’s behavior may differ slightly. In regions where all pumps are E10, the impact is usually small, but it’s still something to be aware of.
Conclusion: For most drivers, the simplest and safest approach is to use the octane recommended by the manufacturer. If you must mix, do so sparingly and be ready to return to a uniform grade to maintain optimal performance.
Summary
Mixing 87 and 93 gasoline will typically produce an octane level somewhere between the two, and for many vehicles it will not cause harm. However, engines that require premium or those operating under heavy load and high temperatures may experience reduced performance or efficiency if the blend falls below the required octane. Always consult your owner’s manual, consider your driving conditions, and be mindful of knock or pinging. When in doubt, refuel with the grade your manufacturer specifies and avoid making a habit of mixing.
Is it okay if I accidentally put 93 instead of 87?
Engine computers can usually adjust their timing to account for the increased octane levels, so if you put premium gas in a regular car, you probably won't notice anything. However, some engines are not designed to burn higher-octane fuel, and you may see a reduction in performance and fuel economy.
What octane gas for Honda CRV?
87
Unleaded gasoline, pump octane number 87 or higher
Use of a lower octane gasoline can cause a persistent, heavy metallic knocking noise that can lead to engine damage.
Is it okay to mix 87 and 93 fuel together?
Yes, and the fuel you end up with will be somewhere between the 87 and 93 octane. Back in the days of electro-mechanical pumps (not dispensers), some of them had a “blend “ feature where you could mix premium and regular in different ratios. Yes.
Is it better to run 93 instead of 87?
If your vehicle is designed to use any of the two, the decision between premium and regular gas comes down to preference. If you want to spend more for better performance and reduced risks of engine failure, then 93 is for you. If you want to save money on gas, then 87 works fine.