Everything You Need To Know About Your 4runner’s Air Filter

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4runner K&N air filter

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The air filter in your 4runner has one important purpose – to allow your engine to breathe while keeping harmful particles out. 

Changing the air filter in your Toyota 4runner is one of the easiest maintenance items you can tackle. A dirty or worn out filter isn’t necessarily going to cause your engine to blow up, but making sure it’s clean will help to keep your 4runner running as efficiently as possible (in terms of both horsepower and MPG)

How often you should change the air filter in a 4runner

There is no set mileage interval for when your 4runner’s air filter should be replaced. It depends greatly on what kind of environment you drive in. It’s best to inspect it visually at every oil change and if it looks dirty, swap it for a new one.

For example, someone who lives on a dirt road out in the middle of nowhere will likely need to replace their air filter more often than someone who lives in a typical city. So it’s really important to consider where your 4runner is driven to know how close of an eye to keep on it. 

In some 4runner owner’s manuals, Toyota recommends replacing the filter every 30k miles. In others, they don’t mention it at all. It’s safer to inspect your specific vehicle than it is to follow a general recommendation that doesn’t take the air your engine breathes into account.

How to know if your air filter is dirty

The easiest way to tell if your air filter needs to be changed is to simply pull it out and take a look. A visual inspection will tell you everything you need to know. 

A worn out filter will look noticeably dirty with black or brown staining. It might even have little chunks of contaminants stuck in it. A filter that’s in good condition will be much lighter in color.

In more extreme cases, a dirty air filter can negatively impact your 4runner’s performance. You might notice slower acceleration or decreased fuel economy. 

These symptoms would require a seriously neglected air filter so they aren’t super common. If you’re experiencing them though, the air filter is a quick and easy thing to rule out.

What’s the best 4runner air filter?

For the longest time, the drop-in K&N reusable air filters were the most preferred among 4runner owners. While they’re still popular today, I thought I’d pop into the T4R forums to see the general consensus. 

Many 4runner owners (myself included) believed that the K&N filters freed up some horsepower and fuel economy, while lasting many years with periodic cleaning. I had every intention of cleaning the K&N that’s currently in my personal 4runner – until I read some very convincing arguments against them.

Next, I asked the viewers of my Canadian Gearhead YouTube channel what filter they’re running in their 4runners. The results were in line with what I was reading on the forums:

Reusable air filters from companies like K&N feature an oiled design. When they get dirty, you can simply clean them, let them dry, then spray a fresh coating of oil on them. Voila! No need to purchase a paper filter ever again. Or so I thought.

I still believe that K&N filters are less restrictive and therefore free up some power. The question is, do these gains come at the cost of proper filtration? It seems like that is very possible. I don’t know about you but my 4runner isn’t a race car – so allowing more dirt into my engine is not worth gaining an extra 0.5 horsepower!

The argument against these filters is mainly focused on the “oiling” aspect though. Many owners have complained of gunky MAF sensors and throttle bodies due to improperly oiled filters. In some cases, the MAF sensor can’t be cleaned and instead has to be replaced to the tune of a few hundred dollars. Suddenly that long-lasting air filter doesn’t make financial sense anymore.

I wasn’t expecting this to happen, but researching for this article has caused me to completely change my own opinions about K&N filters for our beloved 4runners. As a matter of fact, rather than cleaning my existing filter, I’m going to switch back to a paper one. 

The 4.7 V8 is known for its legendary reliability and I’m willing to bet that most of the high-mileage engines continued to use the same type of paper filters Toyota originally put in them.

How to change the air filter on a 4th gen 4runner:

Changing your air filter should take even the most novice 4runner owner no more than 5 minutes. No tools are required either.

First, locate the air box on the passenger side of the engine bay. Your air filter is sitting inside.

There are 4 clips holding the lid of the airbox on. These just snap in and out of place so grab them and pop them loose.

You can leave everything else hooked up and simply pivot the air box lid out of the way enough to squeeze the filter out. Take note of the direction your current filter is facing and make sure to install the replacement the same way.

Slide your new filter into position and clamp the lid back down. Your beloved engine will be breathing freely again!

Do dirty air filters actually perform better?

Surprisingly, a dirty air filter will actually perform better than a brand new one – at least when it comes to filtration. 

Dirt clogs the pores of the filter which in turn, allows less dirt to make it through. So why don’t we throw our new filters on the ground before installing them like a superstitious motorcycle racer does with his new leather suit?

Because a dirty filter will perform worse in every other aspect. It won’t flow as much and if you’re choking your engine out, you’ll experience less power and fuel efficiency. If either of those things matter to you, it’s best to continue replacing your 4runner’s air filter whenever it gets dirty.

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