Subaru Head Gasket Sizing – Everything You Need to Know for Top Engine Performance

If you’re a Subaru owner experiencing engine problems, it’s likely that you’ve come across the term ‘head gasket’ while researching solutions. The head gasket plays a crucial role in ensuring the engine is properly sealed and operates efficiently. However, what many people may not know is that the size of the head gasket can significantly impact engine performance. In this article, we’ll take a comprehensive look at Subaru head gasket sizing to ensure that you know everything you need to know for top engine performance.

Understanding the Function of a Head Gasket

Before diving into the specifics of head gasket sizing, it’s essential first to understand what a head gasket is and its function in a Subaru engine. A head gasket is an essential component that provides a seal between the engine block and cylinder head, preventing oil and coolant from mixing as they flow through their intended paths. A damaged or worn-out head gasket can lead to serious engine problems and, in some cases, complete engine failure.

How Gasket Sizing Affects Engine Performance

As mentioned before, the size of a head gasket can have a considerable impact on engine performance. In a Subaru engine, head gasket size determines the combustion chamber volume, which affects factors such as compression ratio, valve timing, and airflow. Different engines require different head gasket sizes, which is why it’s important to choose the right size for optimal vehicle performance.

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Common Problems Requiring Head Gasket Replacement

There are several common problems that may require a Subaru owner to replace their head gasket. Some of these problems include overheating, loss of coolant with no visible leak, coolant mixing with oil, and low compression. If you notice any of these issues, it’s best to have your head gasket inspected by a licensed mechanic to see if replacement is warranted.

Subaru Engine Specs and Model Types

Subaru engines come in various shapes and sizes, with varying head gasket requirements. Here’s a brief rundown of some of the most popular Subaru models and their head gasket types:

Model Name Engine Type Head Gasket Type
Impreza EJ20, EJ22, EJ25 Multi-Layer Steel (MLS)
Legacy EJ25D, EZ30D Composite
Outback EJ25D, EZ30D Composite
Forester EJ25D, EJ251, EJ253 Composite

Note: This table is not exhaustive and only serves to provide an overview of some of the most popular Subaru models and their head gasket types.

Selecting the Right Head Gasket

When replacing a head gasket, it’s crucial to select the right size for your specific engine to avoid future problems. When searching for a replacement head gasket, be sure to check the manufacturer specifications carefully and choose a high-quality product for the best results. It’s also essential to consider other factors such as the environment in which you drive and the vehicle’s overall condition.

Compatibility of Head Gaskets with Different Models

Subaru head gaskets are not universal, and different models require different sizing. For example, an Impreza head gasket will not be compatible with a Legacy engine. It’s crucial to ensure that the head gasket you choose matches your specific engine type and model to avoid compatibility issues and ensure optimal performance.

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The Process of Replacing a Head Gasket

Head gasket replacement is a complex and time-consuming process that requires expertise and precision. It’s not recommended to attempt replacing a head gasket without the necessary knowledge and equipment. We recommend always seeking professional assistance when replacing a head gasket to avoid potential damage to your engine.


Q: Can a head gasket be repaired, or does it always need replacement?

A: In some cases, a head gasket can be repaired. However, most mechanics recommend replacing the entire head gasket to avoid future problems.

Q: How do I know if I need to replace my head gasket?

A: Some common signs that may indicate the need for head gasket replacement include overheating, coolant mixing with oil, and low compression.

Q: Can I use a different brand of head gasket for my Subaru engine?

A: Yes, as long as the head gasket meets the manufacturer specifications for your specific engine.


In conclusion, proper head gasket sizing is an essential component of optimal Subaru engine performance. Choosing the correct size for your engine type and model can prevent future engine problems and prolong the life of your vehicle. Coupled with regular maintenance and high-quality parts, your Subaru will provide many years of reliable performance.

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Alton Brobst

As a longtime Subaru enthusiast, Alton brings a wealth of knowledge and experience to our blog. From his early days of tinkering with engines to his current role as a certified Subaru technician, Alton has seen it all when it comes to Subarus. When he's not working on cars, he enjoys hiking and exploring the great outdoors.

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