What is the best fuel for a Subaru?
In most Subarus, regular unleaded gasoline with 87 octane is sufficient. Turbocharged models typically benefit from premium 93 octane, and always verify the exact requirements in your owner's manual for your specific year and market.
This article explains how to choose the right fuel for your Subaru by considering octane, ethanol content, and general fuel quality. The guidance below reflects common recommendations across Subaru’s lineup and acknowledges regional variations. Always refer to your vehicle’s manual for your exact model and year.
Octane requirements by engine type
Octane prevents knocking and helps the engine perform as designed. Here is a quick guide, with the caveat that exact figures can vary by model and market.
- Non-turbo Subaru engines (most Impreza, Forester, Outback, Legacy, and certain Crosstrek variants) typically require a minimum of 87 octane. Regular unleaded gasoline is appropriate, and higher-octane fuel does not generally provide a significant performance boost unless the engine experiences knocking on 87-octane under certain conditions.
- Turbocharged engines (such as the WRX and WRX STI) generally require premium gasoline, commonly 93 octane, to maintain peak performance and prevent knocking. If 93 octane is unavailable, some markets may allow a lower-but-still-acceptable grade temporarily, but performance will likely drop and knock resistance can be reduced. Always follow the exact requirement listed in your manual.
- Regional and model variations: Some markets or specific trim levels may have different recommendations. Always check the owner’s manual or official regional guidance for your exact model/year to be certain.
Concluding: Match the fuel octane to the engine design and the manual’s specification. Using a lower-octane fuel than recommended can reduce performance and, over time, potentially harm the engine. If in doubt, opt for the octane your manual prescribes for your exact model and market.
Other fuel considerations
Beyond octane, two additional factors influence fuel choice: ethanol content and overall fuel quality.
- Ethanol content: In the United States, most gasoline is E10 (up to 10% ethanol). Subaru generally supports E10 across most models; avoid higher blends (like E15 or E85) unless your manual explicitly states compatibility. In other regions, ethanol blending varies—always follow local guidance.
- Fuel quality: Top Tier gasoline or similar detergents can help keep deposits to a minimum and support long-term engine cleanliness. While Subaru doesn’t require Top Tier specifically, choosing high-quality fuel from reputable stations is reasonable for optimal performance and longevity.
- Fuel stability and storage: If you store a Subaru for extended periods, consider fuel stabilizers and regular use of fresh fuel to minimize degradation and fueling issues when you restart.
Conclusion: For most owners, use the octane and ethanol level your manual specifies (usually 87 octane with E10 in the US). For turbo models, use premium as recommended. Prioritize good fuel quality and consult the manual for any regional caveats.
Summary
Bottom line: The best fuel for a Subaru depends on the engine. Non-turbo models typically run fine on regular 87-octane gas, while turbocharged models generally require premium 93-octane fuel. In most regions, fuel with up to 10% ethanol (E10) is standard and acceptable, but avoid higher ethanol blends unless your manual confirms compatibility. Always follow your specific model’s owner manual for the most accurate guidance.
Should I use 87 or 89 gas?
Your car will run just fine. All modern cars can run 87,89,91,93. It's suggested that for maximum power that you use 93. If you're not at a track day event and just daily commuting 87 will serve you well. All modern cars are equipped with knock sensors to prevent engine damage from running lower octane fuel.
What happens if I put 93 instead of 91?
Putting 93 octane instead of 91 in a car is generally fine, and you will likely not notice a difference, as the engine's computer will adjust to the higher octane. In some high-performance or tuned vehicles, using 93 may provide a slight increase in performance or fuel economy, though this is not guaranteed. You may be wasting money, as higher octane fuel is more expensive and not needed if your car is not designed for it.
What to expect
- No change: Most modern cars are designed to automatically adjust to the higher octane fuel, so you probably won't notice any difference in performance or fuel economy.
- Potential for slight improvement: In some specific cases, particularly in high-performance or turbocharged engines, the higher octane can provide a slight increase in power or fuel efficiency.
- No harm to your engine: Using a higher octane fuel than recommended is not harmful to your engine.
- Higher cost: You will pay more at the pump for a fuel you don't need.
What to do if your car requires 91 octane
- Check your owner's manual to confirm the minimum octane requirement for your vehicle.
- If your car is not a high-performance model and requires 91 octane, there is no benefit to using 93 octane. You can simply use 91 octane and save money.
- You can continue to use 91 octane for all future fill-ups.
What fuel is best for a Subaru?
For optimal performance, Subaru recommends using 91 or 93 octane premium fuel.
Do subarus run better on premium gas?
Regular gasoline has an octane level of 87 or so, while premium gasoline has an octane level of 90 or above. This can be a huge advantage for luxury and performance cars specifically, like the Subaru WRX and BRZ.
