Can I put 89 gas in my Subaru Impreza?
Yes. For most Subaru Impreza models, 87-octane regular fuel is the minimum, and using 89-octane mid-grade is safe. You likely won’t see a meaningful performance gain from 89 in a typical non-turbo Impreza.
Understanding octane requirements for the Impreza
Octane rating indicates a fuel’s resistance to knocking, a condition that can occur when the air-fuel mixture detonates prematurely in the engine. The Impreza’s owner manuals for current non-turbo models typically specify regular unleaded gasoline with a minimum rating of 87 AKI. Higher-octane fuels can be used, but they usually don’t deliver extra horsepower or better fuel economy in a naturally aspirated engine. If a knock sensor detects detonation, the engine will adjust timing to prevent damage.
What the manual typically says
In most recent Impreza models, 87-octane regular is considered acceptable. You may choose 89-octane mid-grade if it’s what’s available or if you’re driving in unusually hot conditions or on steep climbs, but this is optional rather than required.
Before examining the practical implications, here is a quick overview of how octane works in a typical Impreza.
Key takeaways about octane levels and Impreza fueling:
- 87 AKI is the minimum for most Impreza models; regular unleaded is suitable.
- 89 octane is compatible and safe to use; it generally does not boost performance in a standard NA engine.
- 91–93 octane is not required for a non-turbo Impreza; higher octane fuels cost more and typically offer little or no benefit.
- Always verify the exact requirements for your year and market via the owner's manual or the fuel door sticker.
In summary, 89-octane gasoline is acceptable for most Impreza models, but it is not a guaranteed upgrade over regular 87 octane.
Is 89 octane worth it for performance or reliability?
For a typical non-turbo Impreza, there is usually no significant performance or efficiency gain from using 89 octane instead of 87. The engine’s knock sensor will protect the engine by retarding timing if detonation occurs, which can prevent damage but may negate any potential gains in power. In practice, most drivers won’t notice a difference in everyday driving.
Before you decide to switch fuels, consider these points:
- In normal driving, 87 octane works well and is more cost-effective than 89.
- In very hot weather, on long climbs, or with aggressive driving, 89 may provide a small decrease in knocking risk, but gains are typically minimal.
- Higher-octane fuel costs more per gallon; weigh the cost against any perceived benefit.
For drivers curious about performance differences, the most reliable guidance comes from your owner’s manual and the fuel-filler door sticker on your specific model year and market.
Turbo and performance variants: a cautionary note
If you own a turbocharged Subaru model that’s related to the Impreza lineup, such as the WRX, the fuel requirements are different. Turbo engines generally require higher-octane fuel (often 93 AKI or higher) to prevent knock and maintain performance. Using 89 octane in a turbocharged variant may lead to reduced performance or engine management pulling timing. Always check the exact specification for your vehicle's year and trim.
Bottom line for turbo models
Turbocharged Impreza variants typically need higher-octane fuel than 89; refer to the owner’s manual or the fuel label on the car to confirm the minimum requirement (often 93 AKI).
Practical fueling tips
To make an informed choice about which fuel to use, consider these practical tips:
- Check your owner’s manual and the fuel door label for the exact octane recommendation for your model year and market.
- If you only have access to 89 octane temporarily, you can use it, but plan to return to 87 (or the recommended octane) when possible to minimize fuel costs.
- Be mindful of ethanol content (often E10); most Impreza engines tolerate typical ethanol blends, but very high ethanol levels can affect performance in some climates.
Regular maintenance, such as keeping the ignition system in good condition and using clean, rated fuel, helps ensure optimal performance regardless of octane choice.
Summary
For a typical Subaru Impreza, regular 87-octane gasoline is the standard and usually sufficient. 89-octane mid-grade is safe to use and can be chosen if easier to obtain or if you want a bit of buffer under challenging driving conditions, but it generally does not deliver noticeable power or efficiency gains in a non-turbo engine. If you own a turbocharged variant such as a WRX, higher octane (often 93) is typically required by the manufacturer. Always consult your specific year’s owner’s manual and the fuel door sticker to confirm the exact octane requirements for your vehicle.
