The AEM 28-20304 is a panel-style replacement air filter from AEM Induction, built on the brand's DryFlow washable, non-woven synthetic media. The manufacturer's listing gives an outside footprint of 8.75 in long, 8.563 in wide, and 2.438 in tall, so it is meant to slot into the factory airbox in place of the paper element. Owners on user forums say it seats snugly once the airbox is opened up.
Compared with a stock paper filter, this element can be washed and reused, and the manufacturer says it is designed to last the life of the vehicle. It needs no filter oil, which removes the over-oiling problem that makes reusable oiled panel filters fussy. The manufacturer claims it captures up to 99% of contaminants and holds up in dusty conditions, and it is backed by a limited lifetime warranty. The manufacturer also states that fitting it will not void the vehicle warranty. Any throttle response or horsepower improvement will vary by vehicle and setup, so buy it for filtration durability and reusability, not as a guaranteed power gain.
Fitment: the manufacturer's listing names the 2007-2010 Impreza and 2008-2010 Forester, but other sources show broader year ranges, so confirm your year, engine, and trim with the manufacturer before ordering. Searchers looking for a 07-10 Impreza panel filter upgrade, a 08-10 Forester DryFlow replacement, or a washable no-oil Subaru airbox filter will find this part matches those needs. Installation is a basic drop-in swap, and the steps are covered below.
No. The manufacturer states the filter is oil-free and does not require filter oil, so cleaning is a matter of washing the element and letting it dry.
The manufacturer's DryFlow install sheets call for cleaning the intake filter element every 100,000 miles. Owners on user forums typically wash it more often in dusty conditions.
According to the manufacturer, the DryFlow filter will not void the vehicle warranty.
This is a drop-in panel swap, but the airbox usually has to be opened to seat the element properly. The manufacturer's DryFlow install sheets list a screwdriver and a 10mm socket as typical tools, and they advise disconnecting the negative battery terminal and letting the engine cool if it has run recently. Owners on user forums report the filter fits snugly once the airbox is removed from the engine bay and split apart, and they say that is easier than fighting the clips with the box in place. Check that the element sits flat in the airbox channel and that the lid seals before starting the engine.
