How often do Subaru spark plugs need replaced?
Most Subaru spark plugs on modern engines are designed to last a long time: iridium or platinum plugs are commonly rated to about 100,000 miles under normal use, while copper plugs typically require replacement around 30,000 to 40,000 miles. Turbocharged or aggressively driven Subarus can wear plugs faster, so check your owner’s manual for your specific model year.
Understanding what drives replacement intervals
Replacement timing isn’t a one-size-fits-all figure. It depends on plug material, engine family, turbocharging, and how you drive. Subaru publishes a maintenance schedule tailored to each model year and engine, so the official numbers in your manual take precedence over generic guidance.
Typical mileage intervals by spark plug type
The following ranges reflect common practice across Subaru engines in recent years. Always verify with your owner’s manual and dealer notes for your exact model and year.
- Copper-core spark plugs: commonly replaced every 30,000–40,000 miles in many Subaru engines; some older or lightly driven examples may push toward 60,000 miles in optimal conditions.
- Platinum spark plugs: typically rated for 60,000–100,000 miles, depending on the model and driving conditions.
- Iridium spark plugs: often rated for up to 100,000 miles under normal driving, with some models specifying a 60,000–100,000 mile range.
In general, copper plugs wear faster due to their softer material, while platinum and especially iridium plugs resist wear longer, delivering similar performance over a longer period.
Turbocharged and performance-oriented Subaru engines
Performance-focused Subarus, including turbocharged models, run hotter and experience more intense combustion cycles, which can shorten spark plug life. Subaru’s guidance typically calls for more frequent checks and, in many cases, replacement around 60,000 miles or earlier if you notice signs of wear. Always refer to the model-specific schedule for exact numbers.
Representative engine families and how they influence intervals
Subaru uses several engine families across different generations. Modern FA/FB engines often align with longer 100,000-mile intervals for iridium/platinum plugs, while older EJ-series engines and some turbo variants may have shorter intervals or require copper plugs. The key point is to follow your model’s official schedule and consider driving style when planning replacements.
Signs it’s time to replace spark plugs
Beyond the calendar mileage, certain symptoms can signal worn or fouled plugs. A watchful eye (and ear) can help you catch issues before they impact performance.
- Rough idle, engine misfires, or hesitation during acceleration
- Reduced fuel economy and diminished overall performance
- Check Engine Light or misfire codes (e.g., P0300 range)
- Difficulty starting the engine or extended cranking times
- Visible wear or deposits on plugs during inspection
If you notice these signs, have the plugs inspected and replaced if needed to prevent further engine damage or poor efficiency.
Maintenance tips to maximize spark plug life
Proper maintenance and using the correct replacement parts help extend plug life and maintain performance. Here are practical steps to maximize longevity.
- Always use the OEM-recommended plug type and correct gap for your model
- Torque plugs to the manufacturer specification to avoid thread damage
- Keep ignition components (coil packs, wires) in good condition to prevent misfires
- Avoid unnecessary short trips that prevent full combustion when possible
Regular inspections at your Subaru service interval will help ensure plugs are replaced at the right time and maintain engine efficiency.
Summary
Replacement intervals for Subaru spark plugs vary by plug material and engine type. Copper plugs typically need replacement around 30,000–40,000 miles; platinum plugs often press into 60,000–100,000 miles; iridium plugs commonly reach up to 100,000 miles under normal driving. Turbocharged or high-performance engines may require earlier changes due to higher heat and more aggressive driving. Always consult your owner’s manual for the exact interval for your model year and engine, and replace with the recommended type and torque.
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.
Why are Subaru spark plugs so expensive?
Subaru spark plugs are expensive due to the significant labor involved in replacing them and the cost of the specialized, long-life iridium spark plugs used in most models. The unique boxer engine configuration places the spark plugs on the sides, requiring mechanics to lift the engine or partially disassemble other components to access them. This difficulty and the use of high-quality parts drive up the total cost.
Labor costs
- Difficult access: The boxer engine's flat, opposed cylinders mean spark plugs are located low down near the frame rails, unlike many inline engines where they are on top.
- Time-consuming replacement: Accessing the plugs can require significant labor, such as unbolting the engine from its mounts and carefully lifting it slightly to create enough space.
- Increased hourly rates: The extended time needed for the job results in higher overall labor costs from dealerships or independent mechanics who charge by the hour.
Part costs
- Premium materials: Subaru uses premium iridium or platinum spark plugs, which are more expensive than standard copper plugs but offer a longer lifespan, often exceeding 100,000 miles.
- Precise manufacturing: These plugs are manufactured with high precision to meet Subaru's specific engine requirements, which adds to their cost.
Other factors
- Bundled services: Dealerships sometimes bundle spark plug replacement with other maintenance tasks for the 60,000-mile service, making the final bill appear higher.
- Dealer markup: While the parts themselves are more costly, the primary reason for the high price is the labor involved, and dealership labor rates are often higher than those at independent shops.
Can spark plugs last 100,000 miles?
Less-expensive copper spark plugs have a relatively short lifespan and must be replaced every 30,000 miles or less, while pricier platinum or iridium spark plugs can last up to 100,000 miles.
