The engine dictates the oil: use 0W-20 full synthetic oil for the 2.5L four-cylinder, and 5W-30 full synthetic oil for the 3.6L six-cylinder. Always confirm with your owner's manual or a Subaru service advisor for your exact configuration and climate.
Engine variants and oil requirements
Here are the typical oil specifications by engine option for the 2011 Legacy. Regional differences can exist, so verify against the manual for your vehicle.
- 2.5L DOHC flat-4 (commonly found in base and mid trims): 0W-20 full synthetic oil.
- 3.6L H6 (3.6R models): 5W-30 full synthetic oil.
These are the standard factory recommendations. If you cannot obtain the exact viscosity, use the closest alternative suggested by Subaru in your manual or by a dealer, keeping in mind that significant deviations can affect fuel economy and engine protection.
Oil specifications and capacity
Beyond viscosity, the oil must meet proper specifications and capacity varies by engine. Use a high-quality full synthetic oil with the appropriate API and ILSAC certifications, and avoid mixing viscosities.
- 2.5L engine capacity: Approximately 4.5 quarts (about 4.3 liters) of oil with a filter; use 0W-20 full synthetic.
- 3.6L engine capacity: Approximately 7 quarts (about 6.6 liters) of oil with a filter; use 5W-30 full synthetic.
Always check the exact capacity for your vehicle (including the filter brand) in the owner's manual or on the under-hood oil capacity label, as variations can occur by model year, trim, or aftermarket parts.
Choosing the right oil brand and spec
Look for oils that meet API SN or newer and ILSAC GF-5 (or GF-6 where available), labeled as full synthetic. Subaru-approved or OEM-recommended brands are a safe choice, and many reputable brands offer 0W-20 or 5W-30 synthetics that meet these specs. Using the correct viscosity and a high-quality synthetic helps with engine protection and fuel efficiency.
Oil change intervals
Oil-change intervals depend on oil type and driving conditions. The following guidelines reflect typical recommendations from the era and are commonly used by owners:
- With full synthetic oil: about every 7,500 miles (12,000 km) or 12 months in normal driving.
- With conventional or blended oil: about every 3,000–5,000 miles (5,000–8,000 km), depending on conditions.
- In severe service (extreme temperatures, dusty roads, frequent short trips): shorten the interval accordingly, often to around 3,000–5,000 miles or 6 months.
Always follow the specific intervals listed in your owner's manual and adjust for your driving habits and climate. If in doubt, consult a Subaru service professional.
Summary
For a 2011 Subaru Legacy, oil choice is engine-specific: 0W-20 full synthetic for the 2.5L four-cylinder and 5W-30 full synthetic for the 3.6L six-cylinder. Oil capacity is roughly 4.5 quarts for the 2.5L and about 7 quarts for the 3.6L, with each requiring the appropriate filter. Use oils that meet API SN or newer and ILSAC GF-5 or higher, and adhere to the maintenance intervals printed in your manual. Always verify exact specifications for your vehicle variant and region.