How often should I change the spark plugs on my Subaru Outback?

Spark plug replacement intervals for a Subaru Outback vary by engine type. In general, most non-turbo Outbacks use long-life plugs and can reach around 100,000 miles between changes, while turbocharged models often require changes closer to 60,000 miles. Always check your owner's manual and follow manufacturer recommendations, especially if you drive in harsh conditions or regularly tow, haul heavy loads, or use a severe service schedule.

Engine variants and recommended intervals

2.5-liter naturally aspirated Outback (common in many non-turbo models)

For the 2.5L naturally aspirated Outback, spark plugs are designed for longevity and the maintenance window is typically longer than turbo engines. This is especially true when the vehicle is equipped with iridium or platinum-tipped plugs.

• 100,000 miles: Replace iridium/platinum-tipped plugs under normal driving conditions.


• Shorter intervals may apply if you use copper plugs (less common in newer models) or drive in severe conditions.

In summary, most 2.5L Outbacks aim for a spark plug change around the 100,000-mile mark, though always confirm with your manual and dealer notes for your exact model year and plug type.

2.4-liter turbo Outback (turbocharged FA24 engine, common in newer models)

The turbocharged 2.4L engines with direct injection typically demand more frequent spark plug service due to higher heat and wear. The recommended interval is shorter than the non-turbo variants.

• 60,000 miles: Replace plugs under normal driving conditions.


• Less favorable driving patterns, carbon buildup, or aftermarket plugs may necessitate earlier changes (e.g., around 30,000–45,000 miles).

For turbo Outbacks, plan for a spark plug replacement around 60,000 miles and monitor performance signs such as misfires, rough idle, or reduced power between services.

Older 3.6R H6 Outback (earlier generations)

Some older Outbacks used the 3.6-liter H6 engine, which has its own maintenance cadence that reflects different ignition technology and wear patterns from the newer engines.

• Approximately 105,000 miles: A common target for spark plug replacement on these engines, depending on plug type and wear.


• Always verify with the original equipment torque specs and plug type specified in your owner's manual.

In practice, owners of older 3.6R models should consult their manual or dealer service bulletin for the exact interval, as it can vary by year and plug specification.

Additional considerations

Several factors can affect how soon you should change spark plugs, regardless of engine type. Direct-injection systems are prone to carbon buildup, which can shorten spark plug life. Harsh driving, frequent short trips, towing, or using lower-quality fuel can also accelerate wear. If your engine shows signs of ignition trouble—misfires, rough running, reduced power, or poor fuel economy—it's wise to check the plugs sooner than the scheduled interval.

Summary

For most non-turbo Subaru Outbacks with the 2.5-liter engine, plan for spark plug replacement around 100,000 miles. Turbocharged 2.4-liter Outbacks generally require changes around 60,000 miles, due to higher heat and direct injection. Older 3.6R models may fall near the 105,000-mile mark. Always confirm the exact interval in your owner's manual and consult your dealership or a qualified mechanic if you notice performance issues.

How do I know if my Subaru spark plugs are bad?

One of the first signs of spark plug wear is trouble starting your Subaru. If the engine cranks longer than usual before starting or if you experience intermittent starting issues, it's time to inspect your spark plugs.

How long do spark plugs last on a Subaru Outback?

60,000 Miles
60,000 Miles or 60 Months
Replace the spark plugs.

Do I really need to change my spark plugs at 100,000 miles?

Yes, replacing spark plugs at 100,000 miles is a common and often necessary maintenance task, as many modern vehicles have spark plugs rated to last that long. However, the exact interval depends on your vehicle's make, model, and the type of spark plug installed, so you should always check your owner's manual for the manufacturer's specific recommendation. 
This video explains when to change spark plugs and what happens if you don't: 1mHonest Mechanic ColoradoYouTube · Dec 24, 2023
Why it's important

• Engine performance: Spark plugs that are past their prime can cause rough idling, poor acceleration, and decreased fuel efficiency. 
• Preventing damage: Over time, worn-out plugs can put extra stress on other components, like ignition coils, and may seize in the engine block, making them harder to remove later. 
• Preventative maintenance: Replacing spark plugs is a form of preventative maintenance that can prevent more costly repairs down the line. 

This video explains why it's important to change spark plugs at 100k miles: 52sWhite One Auto, LLCYouTube · May 19, 2021
What to consider

• Owner's manual: Your vehicle's owner's manual is the most reliable source for the correct replacement interval and recommended plug type. 
• Spark plug type: The lifespan of spark plugs varies by material. Iridium plugs are often rated for 100,000 miles or more, while other types like copper or platinum have shorter lifespans. 
• Driving conditions: Severe driving conditions can shorten the life of spark plugs, so your interval may be shorter than recommended if you frequently tow, drive in extreme temperatures, or frequently start and stop. 

How much does it cost to replace spark plugs on a Subaru Outback?

The cost to replace Subaru Outback spark plugs typically ranges from approximately $300 to over $800, with prices varying by model, location, and whether you choose a dealership or an independent mechanic. Dealerships generally have higher labor rates and use OEM parts, leading to a higher price, while independent shops may be less expensive. Newer models with more complex engine layouts can sometimes have higher costs, and labor is often the most significant part of the total price.
 
Factors that influence the cost
This video explains what to consider when buying spark plugs: 30sMrSubaru1387YouTube · Jan 9, 2022

• Location and mechanic: Dealerships and independent shops have different pricing structures. Dealerships typically charge more for labor and use official parts, while independent shops can be more affordable. 
• Engine and model year: The specific model and year can impact the cost. Some engine configurations are more labor-intensive, driving up the final price. 
• Parts: The cost of the spark plugs themselves can vary. Genuine Subaru parts are often more expensive than aftermarket options. 
• Labor: Since replacing spark plugs can be a time-consuming job, the labor cost is often the largest portion of the total bill. 

Examples of recent costs (from customer reports)

• $409: Paid at a dealership for a 2020 Outback. 
• $500+: Paid at a dealership for a 2019 Outback. 
• $300: Paid at an independent shop for a 2019 Outback. 
• $225: Paid at a private mechanic for a 2017 Outback. 
• $275: Quoted for a 2018 Outback at an independent shop.