Mazda MX-5: K&N Air Filter Recharge Kit #99-5000

Took advantage of the beautiful weather this winter day to do some maintenance on the Miata. Today’s project was to clean and recharge my K&N air filter. I bought the K&N #99-5000 recharge kit some time ago with a nice discount from Advance Auto Parts, but didn’t want to do the recharge too soon. Some said it shouldn’t be done before 25k miles others 50k miles. But since I don’t drive my Miata nearly as much as other people with K&N filters on their daily cars (anotherwords that 25k or 50k miles would take me forever) I decided to do the cleaning today.

I’ll say upfront that I didn’t put the K&N panel filter back into the air box after cleaning it, instead I popped the WIX paper air filter back in that only has about 5k miles on it, and left the K&N in the box so that the oil nicely absorbs into the cotton fabric of the filter.

I also took a look at my throttle body and it doesn’t look too oiled up. So that’s a good think, the biggest complaint about K&N air filters is that the oil goes all over the place causing problems. It doesn’t.

This job is fairly simple, though I decided to unscrew a few things to get to the filter easier.

People say that if you don’t take the car offroading than it’s OK to keep the filter in for 25k to 50k miles without cleaning. I obviously never went offroading in my car. But looking at this air box shot and under the hood in general you can clearly see a ton of grime that made it’s way into the engine compartment and that fine grit definitely finds it’s way into the air box.

Interestingly enough there were two large leafs inside the air box.

Doesn’t look too bad, you can see a bit of oily residue on the edge.

The most visible stuff on the dirty side of the filter were dead bugs

The 5k mile WIX air filter went back in while I was doing the cleaning, and it will likely stay in the car for a while, I’ll explain a bit later on as to why…

I followed the cleaning instructions. First I used a soft tip paint brush to get some of the dust and larger debris off the filter before spraying it with the cleaning solution. Left it outside for ten minutes and went in the basement to rinse it off. I used a bucket full of water to dip the filter in first, and then rinsed it under water. But looking up to the light it was clear there were tiny bits of dried lefts still stuck to the metal mesh.

I did not want to leave those little debris in there, so I got a soft plastic stick and gently picked those debris out of there, without poking through or anything just gently brushed up the debris out of the mesh and cleaned it against a rag. Was very happy I did that because I didn’t see any of the YouTube tutorials talking about this.

The tutorials suggested to let the filter dry outside for about an hour. But since it was still a cold day and getting colder towards the evening I decided to leave it outside for a few hours until it was dry.

Final step was straightforward but a bit worrisome for me. How much oil do you actually spray without over spraying? It’s definitely not good practice to put too much oil because that oil would end up in the MAF and throttle body. Which isn’t good… So I gave it sufficient (I think) but not overwhelming spray on each side of the filter. Then put it in the box and will let it sit for a while so it soaks in well before I put the filter back into the air box. I figured this is how the filter was when it was sold to me, who knows how long it sat on the shelf before I bought it, so I’ll leave it out of the car for a while, until I use up my WIX filter and throw it out when I put the K&N back in the car… (probably after the Florida road trip).

Easy peasy!