Parts for your 2009 Subaru Forester-Air filter

2009 Subaru Forester air filter — what it does and how to look after it

Yes, an air filter is absolutely relevant and fitted to the 2009 Subaru Forester. This is confirmed in Subaru’s technical literature, including the 2009 Forester Owner’s Manual (Maintenance and service: Air cleaner element) and the Factory Service Manual for the SH-series Forester, which specify an engine air cleaner element within the intake air box. Many markets, including Australia and New Zealand, also list a cabin/pollen filter in the HVAC system.

The engine air filter’s job is straightforward but critical: it screens out dust, sand, pollen and road grime before air enters the intake, protecting the mass airflow sensor and engine internals. Clean, steady airflow helps the boxer engine run smoothly, maintain power, and keep fuel use and emissions in check. If the filter is clogged, the engine can feel a bit breathless, economy drops, and the Forester may run richer than it should.

As part of regular servicing, the air filter should be inspected at each service under the bonnet and replaced at sensible intervals. Subaru guidance and common workshop practice put replacement roughly in the 30,000–50,000 km range under normal conditions, but in Aussie and Kiwi realities—gravel roads, dust, farm tracks—it can need changing earlier. Think of it as “inspect every service, replace when dirty,” rather than waiting for a fixed kilometre number.

Easy DIY? Too right. Pop the air box clips, lift the lid, note the filter’s orientation arrow, and swap in a quality element. Make sure the sealing lip sits squarely, the box is free of leaves or debris, and the lid’s clips are fully latched. Avoid washing a paper element, and go easy with compressed air (if at all). If choosing aftermarket, stick with reputable brands and be cautious with oiled performance filters, as excess oil can foul the MAF sensor.

Handy signs it’s time to replace:

• Noticeable drop in performance or throttle response
• Worse fuel economy without another clear cause
• Filter looks dark, dusty, or heavily loaded when held to light

Worth noting: this Forester also uses a cabin (pollen) filter behind the glovebox—separate from the engine air filter—so it pays to keep both on the maintenance list for clean breathing inside and under the bonnet.

FAQs

How often should the 2009 Forester’s engine air filter be replaced?
Most workshops in AU/NZ will inspect it at every service and replace around 30,000–50,000 km, sooner if you drive in dusty conditions. If the element looks dirty or airflow feels restricted, replace rather than stretch it out.

Where is the engine air filter on a 2009 Forester?
It sits in the black plastic air box under the bonnet. Release the metal clips, lift the lid, and the rectangular element is right there. Note the orientation when removing and ensure the new filter seats evenly on its gasket.

Does the 2009 Forester also have a cabin/pollen filter?
Yes. Separate to the engine air filter, there’s a cabin filter behind the glovebox that cleans the air coming through the vents. It’s worth checking annually—great for demist performance and for keeping the HVAC tidy.