Permanent air filter?

not really, since there's no advantage, and money and time wasted.

the oem filter is rated for 30,000 miles, then clean or replace. i've never had to replace one because it is so clean when i inspect it, i just tap out any particles and put it back in.

 

The primary purpose of such filters is to clean your wallet.
Unless you drive in dusty conditions, the OE filter can easily last 50,000 miles or more.

 

NO....it is not a "good idea" in any kind of street vehicle.
If you can find the test spec's on them showing what size particles they allow to pass......versus a "stock" filter.......it will be obvious why.

 

I'm guessing from your avatar conditions are a wee bit dustier at your location than ours, so fwiw: our 2010 with 75K kms is still on the original engine air filter, that's pretty close to permanent for me. And it's by no means grungy: you can tell it's not new, there's a slight amount of dust on the ridges, but it looks so good there's no way I'd swap it, it's probably going to make 100K.

And, the K&N filters you oil, they're finicky, I wouldn't mess with them. I had one on a bike, but I wouldn't do it again.

 

I've only seen two test comparisons of air filters and the K&N passed more dirt and larger particles than the OEM it was compared with (this wasn't specific to Prius or Toyota).

I've also seen hundreds of stories of how oil from the filter has contaminated the Mass Air Flow sensor or the throttle body (again not Prius specific).

Your car, your choice.

 

I use a permanent KN cabin air filter. It's much more solid and heavier than what is sold. It's easy to wash.

But the engine air filter? The air filters on the Prius is so easy to change so I don't want to complicate things with oiling, etc... I'm not breathing that air and will just go with what is being sold at Pep Boys.

 

I used the K&N filter for about 2 tanks full of driving. Lots of full acceleration test when merging with freeway. The performance is more noticed in full acceleration. Sound is more lower and deeper but still can be loud. Paper filter is more louder and higher revs. I checked the mass air flow sensor after the 2 tanks and no sign of any oil stains either on the component or on the housing. I also noticed that Toyota has a built in plastic mesh that also show no signs of oil stains. Regarding the fine particles. I can't really see any on the clean side of the filter. But then again I can't really see any directly on the filter itself on the dirty side. I can tell by looking at the rubber seals that the dirty side is dirty and the clean side is clean. I notice that with the OEM paper filter it had a tear spot on it. I think it came that way. So they are very easy to tear. Both filters seem to have lots of fibers on it.

Thanks for bringing up the AFE filter. I notice from their site there is no DRY version for the V only the oiled version. But from Amazon reviews a V owner had good experience with the Prius filter. Amazon: aFe 31-10228 Magnum Flow OER PRO DRY S.

I think at a future time I will give the AFE a try as well. It claims to filter 99.2% of particles and 2 to 1 times better than paper.

Overall when driving with the K&N filter it gives me a little more "confidence" about my car especially when full acceleration is needed. MPG doesn't show any change. It might be a little better. Performance is also a little better.