When should spark plugs be changed on a Subaru Outback?

Spark plugs in a Subaru Outback are typically due for replacement around 100,000 miles (160,000 kilometers) on most modern engines that use long-life iridium or platinum plugs. Turbo models (FA24) follow the same general interval, but you should verify the exact recommendation in your vehicle’s owner’s manual or with a Subaru dealer. If you drive under severe conditions or notice symptoms, you may need service sooner.

This article explains the current guidance for the two main Outback engines, factors that can shorten or lengthen plug life, plug types and installation considerations, and how to tell when it’s time to replace them. The information reflects guidance up to recent model years and can vary by year and trim.

Recommended spark plug replacement by engine

2.5-liter non-turbo (FB25)

For the naturally aspirated 2.5L Outback, the maintenance schedule commonly calls for replacing the spark plugs at about 100,000 miles (160,000 km) under normal driving conditions.

• Interval: approximately 100,000 miles (160,000 km).


• Plugs: use long-life iridium or platinum spark plugs as specified by Subaru’s manual; copper plugs are not recommended for this engine.

Replacement timing can vary by model year and region; always verify with your owner’s manual or a Subaru dealer to confirm the exact specification and torque requirements.

2.4-liter turbo (FA24)

The turbocharged Outback uses a similar long-life plug strategy, with replacement commonly recommended around 100,000 miles (160,000 km) under normal conditions.

• Interval: approximately 100,000 miles (160,000 km).


• Plugs: use long-life iridium or platinum spark plugs as specified; avoid copper plugs in this engine family.

As with the non-turbo engine, consult the exact schedule in your owner’s manual, since sub-model and year changes can alter the recommended replacement interval.

Factors that can affect spark plug life

Several driving conditions and vehicle factors can shorten or extend the life of spark plugs in a Subaru Outback.

• Driving style and conditions: frequent short trips, stop-and-go city driving, or heavy loads can accelerate wear and fouling.


• Weather and climate: extreme heat, humidity, or cold-start heavy use can impact plug longevity.


• Fuel quality and engine health: poor fuel quality, misfires, or oil consumption can foul plugs and reduce life.


• Ignition system wear: deterioration of coil packs or ignition leads can cause misfires and premature plug wear.

If you notice symptoms such as rough idle, misfiring, reduced power, or a drop in fuel economy, have the plugs inspected and replaced if needed.

Plug type, installation and care

Choose the plug type recommended by Subaru for your engine, typically long-life iridium or platinum plugs. When replacing, follow the manufacturer’s installation instructions and torque specifications; avoid using copper plugs for these modern engines unless explicitly approved by Subaru, and follow the manual’s guidance on lubricants and anti-seize application.

Consider having a qualified technician perform the replacement if you are not comfortable with spark plug service, especially on engines with coil-on-plug designs and integrated ignition systems.

Summary

For most Subaru Outbacks, plan to replace spark plugs around 100,000 miles (160,000 km), with the exact interval depending on engine type (2.5L non-turbo vs 2.4L turbo) and driving conditions. Always confirm the exact interval in your owner's manual or with a Subaru dealer, and monitor for signs of wear that could require earlier service. Using the correct long-life plug and proper installation helps maintain performance and fuel efficiency across model years.

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 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. 

How often do spark plugs need to be replaced on a Subaru Outback?

The spark plug replacement interval for a Subaru Outback is typically every 60,000 miles, but you should always consult your owner's manual for the specific mileage recommended for your model and engine type. Some models with turbocharged engines may have a slightly different interval, and long-life spark plugs like platinum or iridium can last longer than conventional plugs. 
Key recommendations

• Check your owner's manual: This is the most accurate source for your specific vehicle's recommended maintenance schedule. 
• 60,000 miles is a common interval: This is the standard replacement interval listed in many maintenance schedules for the Outback. 
• Consider your engine type: Models with turbocharged engines may have a slightly different interval than non-turbocharged models. 
• Long-life plugs: If your Outback has platinum or iridium-tipped plugs, they can last significantly longer, potentially 100,000 miles or more. 
• Preventative maintenance: Replacing spark plugs at the recommended interval can prevent future engine issues like misfires and ensure consistent ignition. 

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.