Any mpg savings from early air filter change?

[m2200b]

I'm aware that filtration improves and for most filters
20-30,000 is a good change interval from a filtration standpoint. But is there any savings on mpg from better airflow of a clean air filter with some loss to better particle filtration?

 

[TimVipond]

The best mpg is from a clean filter. As the filter traps particles, it begins to restrict air flow, but filter particles better. When air flow is restricted to the point that it cannot provide all the air the engine wants, then mpg begins to decline. Dirty air filters can reduce mpg by 10%. Check your owners manual for filter replacement intervals. Many recommend replacement at 15,000 miles.

Another approach is to use an air filter that filters more and smaller particles from the start and holds more particles before air flow is restricted. You can read about such a dry/reusable air filter at http://www.amsoil.com/lit/databulletins/g2235_rev6_06.pdf .

 

[Vaca]

Almost every owner's manual I have seen over the last ten years or so, have a maintenance interval of 30,000 for the air filter.

 

[tripleM]

If you live in a dusty area, then it is closer to now than 30K.

 

[Vaca]

Yes, if the car is driven in a really dusty area, then 30,000 miles is likely too long.

Conversely, if the car is driven only on clean paved roads, then the filter could likely go for many more miles than 30,000. Could go for a 100,000 under clean conditions.

Generally, most manufacturers recommend 30,000 miles.

 

[biomed_eng_2000]

Let's assume:
1. a new filter is $30
2. 10% gas savings after 15k miles
3. $3.00 per gallon
4. car gets 25 mpg

That same $30 can buy you 10 gallons = 250 miles = 2500 miles @ 10% savings. So changing an air filter too early does not save you much money at all.

 

[TimVipond]

Using your numbers, the additional 15,000 miles with a new filter would cost $1830 in gas and filter.
If the last 15,000 miles was 10% less fuel efficient with the old filter, the gas would cost $2,000. Savings with new filter would be $170.

 

[Steve S]

Depends on how much of the air flow is restricted.

 

[PRND3L]

Quote:

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Another approach is to use an air filter that filters more and smaller particles from the start and holds more particles before air flow is restricted. You can read about such a dry/reusable air filter at.

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Here's what amsoil claims:

Better Air Flow
AMSOIL Ea Air Filters allow more airflow than filters that use cellulose media alone. Cellulose fibers are larger than nanofibers, and have larger spaces between the fibers, causing contaminants to load in the depth of the media and plug the airflow path, which results in higher restriction and less capacity. The synthetic nanofibers in EaA Filter media have submicron diameters and small interfiber spaces, which result in more contaminants being captured on the surface of the media and lower restriction.

More Capacity
AMSOIL Ea Air Filters hold up to two and a half times more contaminants than cellulose air filters. Since the nanofibers in the media are so small there are more pores per square inch, allowing for higher dirt-holding capacity and lower pressure drop when compared to cellulose filter media alone. Thinner media fibers produce more uniform pore size distribution, improving the filter’s overall quality and ability to capture and retain particles. Testing shows that Ea Air Filters hold 15 times more contaminants than a wet gauze type filter.


Sooo, can anyone explain:

1) How does trapping particles 'on the surface' as opposed to 'in the depths' of the filter reduce restriction?

2) How does one reconcile the greater capacity claim with the lower restriction claim?

This sounds like marketing doublespeak to me.

Is there a video or something out there to explain or demonstrate these claims?

 

[TimVipond]

The larger particles just pile up on the surface of the filters and on each other. The smaller particles can still go around the larger particles to inbed in the filtration media. Reminds me of the professor who took a glass and filled it with rocks and asked his class if the glass was full. Most every one said "yes". Then the professor took some sand and amazed the students how much sand he could pour in. The Prof said, "now the glass if full".

A student said "no it isn't". He took a can of beer out of his backpack and poured it into the glass, and said "See, it just goes to show, there is always room for beer".

Kind of the same principle.

The Amsoil filter has more smaller pore sizes and less fiber mass due to smaller fiber size. Thus more room to trap smaller particles and more pores to flow so the filter holds more particles before flow is restricted.

 

[PRND3L]

good effort Tim. I'm not convinced, but thanks nonetheless. I'm sure the Eaa is a good product, I'm just leary about amsoil's claims regarding them.

 

[ConfederateTyrant]

By preventing large particles from becoming "stuck" (for lack of a better term) in the filter media, it allows the larger particles to remain on the surface and air can flow around it without excessive restriction. From my understanding, the air will be coming in at a high force, so it would be able to move around the particles better if it's on the surface.

 

[Kestas]

I could never figure out how a dirty air filter can rob a modern car of gas mileage. Modern engines maintain a strict air/fuel ratio for any condition via O2 sensor feedback. All a dirty air filter does is restrict the amount of available air that can be sucked into the engine, thus reducing available top end performance. I fail to see how an engine can burn any more gas with a dirty air filter if the engine maintains the proper air/fuel ratio.

 

[emj145]

Kestas, you bring up an issue that I cannot for the life of me figure out - how does a dirty air filter reduce the mileage of a modern engine? Particularly considering that the very next thing in the intake system is a throttle plate which (except at W.O.T.) INTENTIONALLY restricts the airflow through the intake system.

Most new engines don't just use the O2 sensor to adjust mixture, but measure the amount of air entering the engine as well via an air mass sensor to allow for more rapid adjustment of the fuel/air mixture during throttle position changes. It seems to me that this would allow the engine to operate at an optimal fuel/air ratio even with a substantially dirty air filter.

I would really love to find a way to improve my mileage by 10% simply by changing my air filter more often! Am I missing something?

(By the way, I totally get why dirty air filters used to degrade the mileage of engines with carbs, or even the earlier fuel injected engines which had an "open loop" mode they would go into at wide open throttle when they would run rich on purpose.)

 

[oilyriser]

A dirty air filter might also prevent oil leaks, by running the crankcase breather hose at a lower pressure.

 

[m2200b]

I've got a B2200 Mazda and a 96 3.1 GMV6. The GM panel filter is about 1/2 the size of my B2200 panel filter.
The GM filter not surprizingly get dirty faster than the Mazda's so I change it at 15k and the Mazda at 30K.

 

[Steve S]

Quote:

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good effort Tim. I'm not convinced, but thanks nonetheless. I'm sure the Eaa is a good product, I'm just leary about amsoil's claims regarding them.

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That is how it works with all filters.

 

[Colt45ws]

Im pretty sure cars still go into Open loop WOT enrichment. Max efficency is of course 14.7:1 but max power is at about 12.5:1. I have seen dyno graphs of factory stock modern vehicles going as rich as like 10:1 at WOT. Its to keep the cylinders and cats cool.
As far as filters affecting mileage on a efi vehicle, probably not much. But it will affect power and might eventually cause a CEL. From what I have seen is it affects MAP (speed density) efi systems more than MAF systems. Both the Dodge Ram and my car are MAP and you can really tell when they want a new filter. The F150 is MAF and you cant really tell much difference. I just put a filter restriction gauge on the Dodge, since I dont drive it that often, so theres no guessing when it needs the filter changed. Next free restriction gauge I get is going on the 150.