Parts for your 2010 Subaru Legacy-Spark plugs

2010 Subaru Legacy spark plugs — what they do and when to replace them

Based on Subaru’s 2010 Legacy/Outback owner’s manual, the Subaru service manual, and OEM parts catalogues, spark plugs are fitted to all 2010 Legacy petrol engines (2.5i EJ253, 2.5GT EJ255 turbo, and 3.6R EZ36). The 2.0D diesel variant (where offered) does not use spark plugs, it relies on compression ignition and glow plugs instead. In Australia the model is sold as Liberty, but the hardware is the same.

For petrol 2010 Legacy models, spark plugs are the tiny but mighty igniters that kick off combustion in each cylinder. Fresh, correct-spec plugs help the flat-four or flat-six start crisply, idle smoothly, and deliver proper fuel economy and emissions. Subaru equips these engines with long-life iridium plugs from the factory, so they’re built to go the distance.

Service guidance from Subaru materials indicates replacement intervals typically around 100,000 km for naturally aspirated petrol models, with shorter intervals (often about 60,000 km) recommended for the turbocharged 2.5GT due to higher combustion loads. As always, owners should follow the exact interval and plug specification listed in the owner’s manual and under-bonnet labels for their engine code.

When a 2010 Legacy starts to feel a bit lazy off the line, uses more fuel than usual, or throws a misfire under load, tired plugs are common suspects. Leaving them too long can stress ignition coils and catalytic converters, so timely replacement is smart maintenance.

Best practice is to fit OEM-equivalent NGK or Denso iridium plugs in the exact heat range and reach specified by Subaru. Fine-wire iridium plugs generally come pre-gapped, re-gapping can damage the centre electrode, so the correct approach is to verify the gap rather than force it. On boxer engines there’s limited room to work, so many workshops remove adjacent components for access and change all plugs as a set to keep balance across cylinders.

• Check for oil in plug tubes and cracked coil boots while the plugs are out.
• Install on a cool engine, start threading by hand to avoid cross-threading, and tighten to the factory torque spec shown in service data.
• Avoid anti-seize on modern, plated spark plug threads unless the plug or Subaru specifically calls for it.

Done on time and done right, fresh plugs keep a 2010 Legacy or Liberty running sweet, whether it’s the thrifty 2.5, the punchy 2.5GT, or the smooth 3.6R.

Popular questions about 2010 Subaru Legacy spark plugs

How often should the spark plugs be replaced on a 2010 Legacy?
Subaru schedules vary by engine. Naturally aspirated petrol models are typically around 100,000 km, while the 2.5GT turbo is often due nearer 60,000 km. Always confirm the exact interval in the owner’s manual or service schedule for the specific engine code.

Which spark plug type is best for a 2010 Legacy?
Use the OEM-specified iridium plugs from NGK or Denso in the exact heat range and reach for the engine. These are designed for the boxer’s combustion characteristics and ignition energy, and they deliver long life with stable spark performance.

What are the signs the plugs need attention?
Common clues include rough idle, sluggish acceleration, higher fuel use, hard starting, or an intermittent misfire under load. A scan tool may show misfire counts. If those pop up, inspection and replacement of the plugs as a set is a good move.