Does a 2004 Subaru WRX Really Need Premium Gas?

If you are a proud owner of a 2004 Subaru WRX, you might be wondering if it is really necessary to use premium gas in your car. Is it just a gimmick designed to make you spend more money, or is there a valid reason for using higher-octane fuel? In this article, we will explore the difference between regular and premium gas, the recommended fuel type for a 2004 Subaru WRX, and the consequences of using the wrong type of gas.

Regular vs. Premium Gas

First, let’s start with the basics. Gasoline is a mixture of hydrocarbons that burn in your car’s engine to produce power. The octane rating of gasoline is a measure of its ability to resist knocking or detonation, which is the premature ignition of fuel in the engine caused by excessive heat and pressure. The higher the octane rating, the more resistant the gas is to knocking. Regular gas typically has an octane rating of 87, while premium gas has a rating of 91 or higher.

Recommended Fuel Type for 2004 Subaru WRX

According to the owner’s manual for a 2004 Subaru WRX, the recommended fuel type is premium unleaded gasoline with an octane rating of 91 or higher. The manual also states that using gasoline with a lower octane rating may lead to engine knocking, reduced performance, and possible engine damage in severe cases.

The reason for using premium gas in the WRX is due to its turbocharged engine, which puts additional stress on the engine components. The high-octane fuel helps to prevent knocking and improve engine performance, making it worth the extra cost if you want to get the most out of your car.

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Consequences of Using Wrong Type of Gas

While using regular gas in a 2004 Subaru WRX may not cause immediate damage, it can lead to reduced engine performance, fuel efficiency, and increased emissions. The engine’s timing and ignition system are designed to work with high-octane fuel, so using regular gas can throw off the engine’s balance and lead to knocking or pinging. Over time, this can cause damage to the engine and reduce its lifespan.

Cost Comparison

Many people may opt for regular gas to save money at the pump, but is it worth it? Let’s look at the cost comparison for a 2004 Subaru WRX using regular vs. premium gas.

Assuming an average price of $2.50 per gallon for regular gas and $3.00 per gallon for premium gas, filling up a 15-gallon tank with regular gas would cost $37.50, while filling up the same tank with premium gas would cost $45.00, a difference of $7.50 per fill-up.

While this may seem like a significant cost difference, it is important to consider the long-term effects of using the wrong type of gas. Reduced engine performance and increased emissions can lead to higher maintenance costs and decreased resale value in the future.


Q: Can I use regular gas if premium is not available?
A: While it is not recommended, using regular gas in a 2004 Subaru WRX in an emergency situation should not cause immediate damage, but it can lead to reduced performance and fuel efficiency.

Q: Will using premium gas improve my gas mileage?
A: While using premium gas may improve your engine’s performance, it is unlikely to significantly improve your gas mileage.

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Q: If I use regular gas occasionally, will it harm my car?
A: Using regular gas on a rare occasion should not cause any significant harm to your car. However, repeatedly using the wrong type of gas can lead to long-term damage.

In Conclusion

In conclusion, if you own a 2004 Subaru WRX, it is strongly recommended to use premium unleaded gasoline with an octane rating of 91 or higher for optimal engine performance and longevity. While using regular gas may save you money in the short term, it can lead to reduced engine performance, increased emissions, and higher long-term maintenance costs. Invest in your car’s health and performance by using the right type of fuel every time you fill up.

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Peter Banks

With years of experience as a professional mechanic and Subaru specialist, Peter is one of the most respected members of our team. He's written several articles on Subaru maintenance and repair, and his advice and tips are always practical and helpful. When he's not working on cars, he enjoys cooking and trying out new recipes.

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