08/09 Impreza WRX air filter question

[DriveTOOfast]

Because my new Impreza WRX will be my first turbo car I wanted to double check something.

On past vehicles I have always purchased one of the reusable air filters that you rinse out and oil a couple of times a year.
Is this appropriate for the WRX or is there some reason to keep the factory paper filter?

[jeremy96gase]

Some people think the K&N style filters are not good for our cars because the fluid tends to gunk up the MAF sensor.

However many people run these types of filters and have no problems.

Sometimes, the question of an aftermarket intake comes up when talking about air filters. The consensus on this forum is that the stock intake is very good, and should not be "upgraded" until after other more beneficial mods have been installed (like ECU tuning and and downpipe).

[SD_GR]

There can be no informed answer to that question until the 09 cars are released in sufficient numbers for users to generate adequate oil analysis data.

An air filter's primary goal is to filter intake air (as opposed to simply costing money, making noises, looking nice, or almost but not quite meeting questionable claims of increased power made by those with vested interest in the product...). If an aftermarket filter is a better filter than the stock unit, less dirt will enter the motor, and used oil analysis should provide evidence.

Then there's the question of whether improved filtration in is meaningful -- if the stock unit is adequate, by definition no improvement is necessary. That is, if the stock unit, serviced correctly, works well enough to protect the motor throughout the motor's expected service life, then a better aftermarket filter is still a waste of money.

In the previous generation cars, the stock filter was excellent and a functioning stock intake system provided great protection -- a look at used oil analyses here and elsewhere proves this. in fact, once one sees a few results, it becomes easy to spot a problem in the air filter -- or an aftermarket air filter -- and that IMO is very telling in and of itself.

[wrxperformance]

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[silver03]

Stick with the stocker. I have a K&N in our WRX and an AVO in our LGT. (Both panel filters) Soon I will replace both with stock filters. Performance Difference is so marginal..