The Great air filter debate - my findings & observations

[danimerciss22]

Trudat, however, I don't consider 5-6mpg a "dramatic" improvement, just an improvement nonetheless, especially for a 15 year old beast like mine

 

[BigOleFordFan]

UPDATE 5/21/25​

I just got back from an 1100 mile round trip, ~97% highway driving at an avg of 60-70mph, with a brand new MAF and managed to get an avg of 17.8mpg.....

So even though I had cleaned the old but original MAF and it looked ok, the new one seems to have helped a little more, in addition to continuing with the high-end filter, fresh full Synth 5w30 oil, extended-life Fram oil filter, and 93 Super gas all the way.....

I also added a can of Seafoam High Mileage fuel & oil treatment at each fill up, just out of curiosity more than anything else, and it did not seem to hurt anything

 

[ManUpOrShutUp]

UPDATE 5/21/25​

I just got back from an 1100 mile round trip, ~97% highway driving at an avg of 60-70mph, with a brand new MAF and managed to get an avg of 17.8mpg.....

So even though I had cleaned the old but original MAF and it looked ok, the new one seems to have helped a little more, in addition to continuing with the high-end filter, fresh full Synth 5w30 oil, extended-life Fram oil filter, and 93 Super gas all the way.....

I also added a can of Seafoam High Mileage fuel & oil treatment at each fill up, just out of curiosity more than anything else, and it did not seem to hurt anything

For comparison, I'm at just shy of 220k miles, 87 octane, original MAF, 5W-20 syn blend, standard Motorcraft oil/air filters, no fuel treatments, 87 octane and a mix of local/highway (~80 mph) driving (more local than highway) ... 16.4 mpg. All of that is to say I don't think anything you've done has hurt anything, but it doesn't seem like it's offered much, if any, MPG benefit either. The 93 octane cost you an extra $49.44 as well, based on the current averages of 87 vs 93 in PA. If we were to (just for the sake of discussion) pretend that you would gotten 16.4 mpg with 87, the 93 still cost you an extra ~$31. That doesn't even account for the extra money spent on everything else. All of that is to say, any potential MPG benefits (if there are actually any) are costing you more than than they are worth.

 

[Fastcar]

For comparison, I'm at just shy of 220k miles, 87 octane, original MAF, 5W-20 syn blend, standard Motorcraft oil/air filters, no fuel treatments, 87 octane and a mix of local/highway (~80 mph) driving (more local than highway) ... 16.4 mpg. All of that is to say I don't think anything you've done has hurt anything, but it doesn't seem like it's offered much, if any, MPG benefit either. The 93 octane cost you an extra $49.44 as well, based on the current averages of 87 vs 93 in PA. If we were to (just for the sake of discussion) pretend that you would gotten 16.4 mpg with 87, the 93 still cost you an extra ~$31. That doesn't even account for the extra money spent on everything else. All of that is to say, any potential MPG benefits (if there are actually any) are costing you more than than they are worth.

Since we are still on this. Checked the MPG using the info from the truck and it showed 18.9 mpg. Thats a combination of about 50% highway and 50% city. Also using 87 octane, with 373 gears on a 4x4 Stealth. These thing weren't made to be economical.

 

[NorthernExMax]

My .02 from reading this thread-
OP never informed us if his old filter was clogged, which could partially explain the large increase in MPG’s (though still within oem/stock expectations).

A shorter filter than OEM will actually cause a decrease in power. For a slight crash course on this, we found with my ecodiesel that the wix/napa/most aftermarket drop in filters were the filters for the HEMI/pentastar engines. The Ecodiesel air filter has the same dimensions length/width, but is about 3/8ths of an inch thicker than the other engines. This results in a lower power, lower MPGs and such of the diesel engine. So to go with a thicker filter than OEM would increase your flow/efficiency. A more porous filter (cotton-types) will typically not be thicker, but more open which will also increase efficiency.

Now onto my biggest point- alot of these modifications do not ADD efficiency to your engine, these are modifications i would say RESTORE efficiency to your engine, as the design of them on the lot takes into more items of consideration than just efficiency. Engine noise, cost, and then efficiency are going to be the 3 things they need to mix together, fairly equally, so that many different people will be interested in purchasing them and at good prices (though that is relatively out of the window as of late). The intake resonators, intake horn at the airbox (gotts mod), are a couple examples of efficiency that was sacrificed for a quieter engine and reduction in power.

If engineers were to build a vehicle that lasted forever with cheap parts at maximum efficiency, nobody would need to buy another vehicle again. Hence why EOL planning is part of the design.

If a paper air filter costs $3, and an oiled cotton filter costs $30, they would be selling 10 trucks for the same price they would sell 100 trucks. The math there shows for their initial sale/manufacture, it isnt feasible for everything to come equipped with a quality air filter, but for the person interested in maximizing the efficiency of their vehicle, i would say an oiled cotton filter is definitely the way to go for a N/A engine.

The filtration, explained. Coarse and fine dust efficiency (paper filters test for fine because they can filter out the fine particulates easily, whereas the oiled/dry cotton media filters do an excellent job at filtering coarse particles, but not fine particles, hence why they claim 99% efficiency, but don’t say it is only for coarse debris). Now, onto why this is important. There is nowhere in the 5.4 engine that fine debris will be a problem, the tightest tolerances in the intake track happen to be very large (think intake valve, throttle body) and you will not have a problem there. Those with turbos or superchargers have much tighter tolerances (look up turbo dusting, and this is a legit problem) and MIGHT see adverse effects from a cotton media filter, but this is also unlikely.

I myself prefer the protection on turbocharged engines so i have an aftermarket paper filter on my diesel, but when the filter is due to be replaced on the expedition, a drop-in K&N is coming down!

 

[BigOleFordFan]

OP never informed us if his old filter was clogged, which could partially explain the large increase in MPG’s (though still within oem/stock expectations

My old air filter was NOT clogged, as I change them on a regular basis, usually at every other oil change...I don't know exactly what the original MPG spec was, but I suspect it was in the range I am getting now, ~16-18, but was ~10-12 before the mods

These are modifications i would say RESTORE efficiency to your engine

That was my goal from day 1, so I consider it achieved, since my vehicle is approaching 16 years old and I mainly wanted to see if I could regain some MPG (and/or other benefits), which they did.....

And with that, I say thank you to everyone who contributed to (or will contribute to) this discussion. I appreciate all of the feedback, comments & suggestions

 

[Fastcar]

Interesting read. I figure that most production factory hot rods do not use a oiled filter. They spend a crazy amount of money testing trying to go fast. I've yet to by a vette with an oiled filter or any other performance car with a oiled filter. Why does anybody think that is? Further on the econo box's where mileage is king what type of filter is oem?
Regarding k&n don't be quick to fall for a marketing show.

 

[Fastcar]

My old air filter was NOT clogged, as I change them on a regular basis, usually at every other oil change...I don't know exactly what the original MPG spec was, but I suspect it was in the range I am getting now, ~16-18, but was ~10-12 before the mods

That was my goal from day 1, so I consider it achieved, since my vehicle is approaching 16 years old and I mainly wanted to see if I could regain some MPG (and/or other benefits), which they did.....

And with that, I say thank you to everyone who contributed to (or will contribute to) this discussion. I appreciate all of the feedback, comments & suggestions

As long as your happy, I'm happy!

 

[NorthernExMax]

Interesting read. I figure that most production factory hot rods do not use a oiled filter. They spend a crazy amount of money testing trying to go fast. I've yet to by a vette with an oiled filter or any other performance car with a oiled filter. Why does anybody think that is? Further on the econo box's where mileage is king what type of filter is oem?
Regarding k&n don't be quick to fall for a marketing show.

To be fair, the oiled cotton media came about long ago, when oem filters were trash. Nowadays, you have 2 options for performance, IF that is not what the setup was designed for.

1- larger filter media/more filter surface area.

2- more porous filter media

The first option is the best option, and is what you see on things like hellcats, mustangs, probably corvettes, and other high-performance vehicles where performance is #1 goal. Check out the difference between a scat-pack challenger and a powerwagon ram. Same engine, challenger has a deeper and larger filter than the ram, resulting in improved airflow. This is where you usually have to change out hard parts to accomodate a much larger filter.

If you are not wanting to change out your parts, the next best option is to see what the biggest or best flowing filter would be that fits in your factory airbox is going to be your upgrade. For the expeditions, i am only aware of the cotton media filters that flow more air than the stock system.

There are other vehicles out there obviously, some that i am aware of, that have a similar “easy upgrade” because of the cookie-cutter approach “we use this on this vehicle for this engine, lets use it for all others” or any other nonsensical reasoning for why engineers don’t prioritize efficiency over everything else when designing parts for these. Like, why would anyone think it is a great idea to incorporate the exhaust manifold into the pentastar engine? Or the fact that the 5.4l and the 6.8l engines have the same air filter in excursions, even though one very much obviously is bigger than the other?

Guess they have everything right from the factory…

 

[BigOleFordFan]

I don't know exactly what the original MPG spec was, but I suspect it was in the range I am getting now, ~16-18

Well, after looking thru my time of sale documents, I found the original window sticker that indicated that the factory rating was ~16-18 mpg, back in 2010 when it was built...

So now that I am back in that range, I am a happy camper... ....

 

[GaryH]

We're gonna test that:

Which Car Air Filter is Best? Let's find out! Fram, K&N, Wix, Purolator, & AC Delco showdown

Best car air filter showdown: Fram Extra Guard, K&N Performance, Purolator, Wix, AC Delco, and EP Auto. Performance testing: filtering particles 5 microns an...

youtu.be

 

[NorthernExMax]

We're gonna test that:

Which Car Air Filter is Best? Let's find out! Fram, K&N, Wix, Purolator, & AC Delco showdown

Best car air filter showdown: Fram Extra Guard, K&N Performance, Purolator, Wix, AC Delco, and EP Auto. Performance testing: filtering particles 5 microns an...

youtu.be

Video was from 5 years ago, just this year WIX changed manufacturers, as well as he does prove that the K&N outflows all other filters, and then decided to give his opinion why it did a good job of filtering (even though he sprinkled flour on everything, which I am not really sure that is a good representation of contaminants).

TLDR: K&N performed best as a performance filter but did not perform best at filtering out his contaminants, which isn’t what K&N claims it would do anyways

 

[k4vbb]

Trudat, however, I don't consider 5-6mpg a "dramatic" improvement, just an improvement nonetheless, especially for a 15 year old beast like mine

But regardless, the mfgr's would NEVER do this, as it would cost them a few extra pennies, which of course, would be amplified by about 20,000% and passed on to us consumers

This would be a VERY significant increase to a manufacturer and would wind up SAVING them tons of cash. While this is not the only EPA standard a manufacturer strives to meet, the CAFE standard adds up the fuel savings for an entire fleet of vehicles. The way it works is that if a given vehicle produces a reduction in fuel consumption, no matter how small, that savings is added up for the entire fleet of that vehicle. For example, if an F-150 gets .01 better miles to the gallon, that .01 is added up for the entire fleet of 800,000 (random guess) F-150's that were produced in that line. This is expected to save ~8000 gallons of fuel for that fleet over a given period of time. And for that, the EPA gives the manufacturer a significant tax break on the production of that vehicle.

I'm glad you're getting good results. Personally, however, I avoid oiled air filters on vehicles that have MAF sensors.

 

[Fastcar]

Video was from 5 years ago, just this year WIX changed manufacturers, as well as he does prove that the K&N outflows all other filters, and then decided to give his opinion why it did a good job of filtering (even though he sprinkled flour on everything, which I am not really sure that is a good representation of contaminants).

TLDR: K&N performed best as a performance filter but did not perform best at filtering out his contaminants, which isn’t what K&N claims it would do anyways

I'm waving the BS flag. Talking about 0 -60 and a difference of a tenth of a second. That is an uncontrolled test. Too many variables.

 

[BigOleFordFan]

I'm waving the BS flag. Talking about 0 -60 and a difference of a tenth of a second. That is an uncontrolled test. Too many variables.

Agreed, but regardless of what they said, I was NOT interested in/focused on, nor did I claim any 0-60 improvements, of which a tenth of a second wouldn't even be noticed by or important to anyone other than a professional race car driver, and AFAIK, they DON'T run Expy's in drag races, however that might be something to see in person if the possibility existed...

And also, my test was for my personal Expy, so I don't give a rat's ass about "fleet" savings or performance, so I'm not sure why that was even brought into the discussion, but oh well....

 

[Fastcar]

Agreed, but regardless of what they said, I was NOT interested in/focused on, nor did I claim any 0-60 improvements, of which a tenth of a second wouldn't even be noticed by or important to anyone other than a professional race car driver, and AFAIK, they DON'T run Expy's in drag races, however that might be something to see in person if the possibility existed...

And also, my test was for my personal Expy, so I don't give a rat's ass about "fleet" savings or performance, so I'm not sure why that was even brought into the discussion, but oh well....

Perhaps somebody works for a filter company? They are sneaky little devils ya know.

 

[GaryH]

I bet you would consider it significant if you LOST 5-6 mpg.

 

[NorthernExMax]

I bet you would consider it significant if you LOST 5-6 mpg.

Pretty sure if you lost 5-6 mpgs from a filter swap you got some more serious things going on buddy

 

[BigOleFordFan]

I bet you would consider it significant if you LOST 5-6 mpg.

Ummm.... if I wanted to lose 5-6mpg, I wouldn't be fiddling with filter changes, all I'd have to do is put the pedal to the metal a few times here & there, and BOOM, 5-6mpg (or more) gone, gone & gone, hahahaha