Which engine oil is best for a Subaru Legacy?

The best engine oil for most Subaru Legacy models today is a full-synthetic 0W-20 that meets API SN or newer specifications and ILSAC GF-5/6. This viscosity supports fuel economy and reliable cold-start protection for contemporary engines.

In practice, the right oil depends on your specific Legacy model year, engine variant, climate, and mileage. Always verify the exact viscosity and spec in your owner's manual or with a Subaru service adviser. The guide below explains how to navigate common Legacy configurations and how to choose oils that keep your engine clean, efficient, and within warranty requirements.

Understanding Subaru’s oil standards

Subaru generally emphasizes synthetic oils that meet current API and ILSAC performance categories, with 0W-20 standing as the default for most contemporary Legacy engines. Climate, driving style, and engine age can influence whether a different viscosity is acceptable or preferred. The key is to select an oil that matches the manual’s specification and to follow Subaru’s recommended change intervals.

The following overview highlights the core considerations when selecting oil for a Legacy:

• Viscosity: 0W-20 is the standard for most modern Legacy engines; 5W-30 (or 0W-30 in some climates) may be acceptable if the manual allows it or if you own an older engine.


• Performance spec: Look for oils that meet API SN (or newer) and ILSAC GF-5 or GF-6.


• Oil type: Full synthetic is strongly preferred for durability and clean pistons, seals, and turbocharging protection (where applicable).


• Manufacturer guidance: Always follow the viscosity and spec listed in the owner’s manual for your exact model and year.

In short, the best practice is to choose a 0W-20 full synthetic that meets API SN+/GF-5 or GF-6 specifications and to confirm with Subaru’s manual for your year and engine.

Engine variants and their oil needs

2.5L four-cylinder engines (common in later Legacy models)

For most 2.5L Legacy engines found in recent years, Subaru and most enthusiasts favor 0W-20 full synthetic oil that meets API SN or newer and ILSAC GF-5/ GF-6. This combination supports cold starts, fuel efficiency, and reliable protection across a wide range of climates. If you drive in consistently high temperatures or have a very old engine that the manual allows for an alternative, a 5W-30 may be used as directed by the manual or dealer guidance.

• Recommended viscosity: 0W-20


• Recommended spec: API SN+/ILSAC GF-5 or GF-6


• Oil type: Full synthetic


• Notes: Check the manual for any climate-specific allowances or updates from Subaru

Following the manual’s guidance on change intervals and using a quality full synthetic will maximize efficiency and longevity for the 2.5L engine.

3.6L flat-six engines (found in older Legacy trims)

Earlier Legacy models with the EZ36 3.6L engine commonly used a heavier viscosity, often 5W-30, especially in hotter climates or older service schedules. If your Legacy is equipped with this engine, confirm the exact viscosity and spec in the owner’s manual or with a dealer, as some years allow for 0W-20 or require 5W-30 depending on climate and maintenance history.

• Recommended viscosity (typical guidance): 5W-30 (verify for your year)


• Recommended spec: API SN+/ILSAC GF-5 or GF-6


• Oil type: Full synthetic or high-quality conventional if explicitly allowed by the manual


• Notes: Climate and model-year variations are common; manual is the ultimate reference

For older 3.6L Legacy engines, sticking to the manual’s specification is particularly important to avoid issues with tolerances and long-term wear.

How to choose oil and brands that fit a Legacy

Choosing the right oil brand and product is about matching the specification, viscosity, and your driving conditions. The following guidance helps you shop confidently.

Oil options and selection tips:

• Viscosity and spec alignment: Choose 0W-20 full synthetic that meets API SN+/ILSAC GF-5 or GF-6, unless your manual specifies an alternative viscosity.


• Quality brands: Reputable full-synthetic oils from brands like Mobil 1, Castrol, Pennzoil, Valvoline, Shell, and others typically offer 0W-20 formulations that meet the required specs.


• Filters and kits: Use a quality oil filter (OEM or equivalent aftermarket) and consider a new drain plug gasket when you change oil.


• Certification and packaging: Look for current API certification marks and GF-5 or GF-6 labeling on the bottle.

In practice, many Legacy owners choose a widely available 0W-20 synthetic from a reputable brand to simplify maintenance and ensure compatibility with Subaru’s warranty expectations.

Maintenance tips and oil-change intervals

Oil-change timing is influenced by driving conditions, climate, and whether you’re using synthetic oil. Always follow the owner’s manual and the vehicle’s Oil Life Monitor (if equipped). The following guidelines reflect common practice for modern Subarus, but confirm your exact interval in the manual.

• Normal driving with synthetic oil: an interval around 7,500 miles (12,000 kilometers) is common, but many manuals permit 6,000–7,500 miles depending on model year and driving conditions.


• Severe driving conditions: shorter intervals, typically around 3,750–5,000 miles (6,000–8,000 kilometers), or as indicated by the monitor if equipped.


• Monitor usage: if your Legacy has an Oil Life Monitor, follow its recommendations for the exact change timing.

Regular oil changes with the right synthetic oil help maintain engine performance, fuel efficiency, and longevity. Always reference the manual for the exact intervals and specifications for your particular year and engine.

Summary

For most Subaru Legacy owners, the best engine oil is a full-synthetic 0W-20 that meets API SN or newer and ILSAC GF-5/6, aligned with the vehicle’s manual. This holds true for many 2.5L engines across recent model years. Some older or climate-specific configurations—such as certain 3.6L engines—may require 5W-30 or another viscosity as specified by the manual. Always consult your owner’s manual or a Subaru service advisor to confirm the exact viscosity and spec for your year and engine, and use a reputable synthetic brand with a quality filter. Following the recommended change intervals helps keep your Legacy running smoothly for years to come.

Is it okay to use 5w30 instead of 0w20?

It is not ideal to use 5W-30 instead of 0W-20, as 5W-30 is thicker and could negatively impact fuel economy and potentially increase wear in modern engines designed for the thinner 0W-20 oil. While it may not cause immediate damage, long-term use of a heavier oil grade can lead to reduced efficiency and strain on certain engine components. 
Potential consequences of using 5W-30 in an engine designed for 0W-20 

• Reduced fuel economy: Thinner oils like 0W-20 are specified for their lower viscosity, which helps improve fuel efficiency. Using a thicker oil can slightly decrease fuel economy. 
• Increased wear on startup: A heavier oil takes longer to circulate at cold temperatures, which can increase wear on engine parts, especially during cold starts. 
• Engine stress: Modern engines with 0W-20 oil use precise specifications for things like oil flow and pressure. Using a thicker oil may cause components like the timing chain tensioners to not receive the correct pressure. 
• Potential for issues in some modern vehicles: Some modern vehicles with 0W-20 oil may even trigger a check engine light because their engine control modules (ECMs) detect the thicker oil. 

When it might be a different story

• Older engines: Some older engines might have been designed with 5W-30 as a recommended viscosity, and in some cases, the thicker oil can even reduce oil consumption in engines that have developed wear over time. 
• Extremely hot climates: In very hot climates, some mechanics suggest that a 5W-30 oil might be a better choice for high-temperature protection. However, it's still best to check your owner's manual to see if 5W-30 is listed as an acceptable alternative for your region. 

Conclusion

• Always check your owner's manual: Your owner's manual is the most reliable source for oil type recommendations. 
• Use 0W-20 if specified: If your vehicle's manual specifically calls for 0W-20, it's best to stick with it to ensure optimal performance and longevity. 
• Consider 5W-30 only if recommended: If your owner's manual allows for 5W-30 as an alternative or if you are in a very hot climate and the manual permits it, you could consider using it. 

What kind of oil does a 3.7 L V6 take?

Capacities and Specifications - 3.7L

Name	Specification
Recommended motor oil (U.S.): Motorcraft® SAE 5W-20 Premium Synthetic Blend Motor Oil XO-5W20-QSP	WSS-M2C945-A
Recommended motor oil (Canada): Motorcraft® SAE 5W-20 Super Premium Motor Oil CXO-5W20-LSP12	WSS-M2C945-A

What oil should I put in my Subaru Legacy?

The Subaru Legacy requires either 0W-20 synthetic oil for newer models (roughly 2013-present) or 5W-30 synthetic oil for older models, turbocharged engines, and 6-cylinder engines. Always check your owner's manual for the exact specifications for your vehicle's year and engine to ensure you get the correct type and viscosity. 
Oil type by model year and engine

• 0W-20 Synthetic: Generally recommended for 2013 and newer, non-turbocharged models. 
• 5W-30 Synthetic: Typically used for older models (approx. 2005-2010) and for turbocharged engines or 6-cylinder engines, regardless of year. 

Important considerations

• Consult your owner's manual: This is the most reliable source for determining the correct oil type for your specific vehicle. 
• Check engine type: The engine size and whether it is turbocharged will affect the recommended oil. 
• Use synthetic oil: Subaru recommends synthetic oil for optimal performance and protection, especially for newer and turbocharged engines. 

Why does Subaru recommend 0W20?

Subaru uses 0W−200 cap W minus 200𝑊−20 oil in its non-turbocharged engines because its low viscosity improves fuel economy and reduces friction, while also providing excellent protection across a wide range of temperatures. This specific oil is formulated to work with the low-friction design of these engines and is optimized to help them operate efficiently and last longer. 

• Improved fuel efficiency: The thinner viscosity of 0W−200 cap W minus 200𝑊−20 oil allows it to flow more easily, reducing drag and leading to a slight improvement in miles per gallon. 
• Enhanced cold-weather performance: It flows more readily in cold conditions than higher-weight oils, which helps with faster lubrication and less wear when the engine is starting up. 
• Optimized for engine design: Subaru formulates its 0W−200 cap W minus 200𝑊−20 oil specifically for its non-turbocharged engines to work well with their low-friction design and ensure optimal performance and longevity. 
• Consistent viscosity: Synthetic 0W−200 cap W minus 200𝑊−20 oil is designed to maintain its viscosity across both hot and cold weather extremes, preventing breakdown and providing consistent protection.