Study on Air Filter Condition and Fuel Economy

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Originally Posted By: TrevorS
Just found this so haven't read through it in detail.

I found it because Purolator are claiming a clean air filter can give 11% better acceleration, which turns out to be true in one instance of WOT testing.

But apart from that, there are plenty of tests and measurements in this study for air filter enthusiasts to enjoy.

http://www.fueleconomy.gov/feg/pdfs/Air_Filter_Effects_02_26_2009.pdf

The real question should be "compared to what"? I could imagine a heavily loaded filter can create problems, but modern cars don't have those issues unless the filter is heavily restricted.
 
So for fuel economy, all the lists for 10% better fuel economy come from the old study from the 80s that was done with carbureters (also from oak ridge, DOE).

That study was referenced for about 20years, and why 10% fuel economy from air filters has been in MPG checklists, and then circularly get referenced. If you try to backtrack references, they all eventually point back only to the old study.

So while this new updated study got published 2009, but all the old tips never die and the links still just linger around.

For clogged filter, they have pictures in the report on what is a clogged filter. Basically it loks like they wrap or layer over the entire filer with multiple layers of shop towels and paper towels to represent "severely clogged". But it is scientifically measured and amount of wrapping or layers calibrated to represent a specific amount of pressure drop compared to clean filter. so you can reproduce this at home if you want.

From the picture it looks to be about 2shoptowels and 1 paper towel represents the severely clogged.
 
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"Despite the filter restrictions, however, no significant changes in fuel economy were observed."

That's exactly what a knowledgeable car guy would expect. And the opposite of what advertisements claim and the uninformed believe.

The part of the report that surprised me was the 1972 car only suffered a 2.7% decrease in economy with a clogged filter. The 'severely clogged' filter raised that to over 7%, but the car was almost undrivable.

The 'severely clogged' filter was extreme. It had far more restriction than would occur in real life. In most cases the engine vacuum at highway speed actually twisted the filter until air bypassed it.
 
I found it interesting that the new OEM filter had far more restriction than aftermarket. And that aftermarket had only slightly more restriction than performance.

Pity they didn't name the brands
 
Originally Posted By: y_p_w


I found it because Purolator are claiming a clean air filter can give 11% better acceleration, which turns out to be true in one instance of WOT testing.

The real question should be "compared to what"? I could imagine a heavily loaded filter can create problems, but modern cars don't have those issues unless the filter is heavily restricted.


This is a great and useful study.. one which I have linked to a many times since I found it in '09.

I think they mean 11 percent better acceleration than with the filter at it's maximum rated restriction (they probably selected a specific example because some cars might be more or less effected by filter restriction). That's entirely plausible. Less and less do you see any specific MPG claims. That is good.

The other thing this study tells me is that a low restriction/performance filter element isn't going to give you any better than a tiny or fractional increase in fuel economy. Despite "conventional wisdom" (read "ad hype" ) saying otherwise. A full tuned system MIGHT, but an element alone... not bloody likely.

The the low 2.7% drop on the carbureted car surprised me also at the time because, as noted above, the old standby number was always ~10 percent. I have an old study somewhere (may be the one referenced) but I don't recall it in detail. It's very likely that 10% was the maximum number ... but it may vary according to the individual engine and carburetor.

So now you guys have experienced the same mind-opening that started me on the restriction gauge bandwagon I currently ride. We know that fuel economy on an EFI engine is not much effected by restriction but we know peak power IS, at least at some point in the gradual loading up of the filter. It just depends on how much flow excess the filter has over the airflow required to make maximum rated power. The engine manufacturers probably have an exact restriction number for that point but I'd bet the generic numbers are pretty close, if not on the conservative side.
 
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My only negative about the restriction gauge is that i suspect it would invalidate my manufacturers warranty. And i am unlikely to keep this Jaguar past the end of the warranty.

Though with a new good quality filter i have no more dpf lights coming and and the round town economy has improved by at least 5mpg going by the last 500 miles of use.

It also seems to have a bit more responsiveness at low throttle settings, which with 440 ftlbs of torque is most of the time round London.
 
I haven't read that article completely yet.

But as a really dirty filter seems to have had detrimental effects on my vehicle as far as emissions go due to the dpf issues i was having would the data in that report be more informative if they also measured the exhaust emissions at the same time?

I apologise in advance if that was mentioned in the article as i haven't finished resding it yet.

Also a pity they didn't do the same for a turbo diesel.

Perhaps somebody will as they become more prevalent in the US.
 
bigjl: Different ballgame with diesels. Fuel economy is MOST DEFINITELY effected with a diesel... more so with older diesels (mechanical) than with electronic and common rail. The fuel system on the older diesels is calibrated to a certain amount of air. Reduce that with a plugged filter and the injection system still pumps in the same amount of fuel regardless. The electronic diesel can compensate somewhat but not as much as a gas closed loop EFI system, so their economy goes down with a plugged filter as well.The article mentions that they hoped to do a similar test on diesels but I haven't seen it yet.

Emissions on a gas engine wouldn't change either... at least to the point that driveability is grossly effected. I believe that is mentioned in the story as well, if not specifically, then as a side note.

Not sure why the installation of a restriction gauge would effect your warranty but I guess you don't have the Magnusson-Moss Warranty Act working for you in Britain.
 
We certainly don't Jim.

Only a few years since the EU Block Exemption came into effect allowing car owners to use other reputable and vat registered garages from doing routine maintenance as they used to void the warranty for that or at least void the warranty for any system worked on outside the dealer network.

Manufacturers are getting round this by giving two year EU wide warranties with the third or more years being a "dealer" warranty, no full dealer history and no warranty whatsoever after the first part.

They really are somewhat sneaky in the EU these days.
 
We have also seen a big problem on Hino trucks at work with dirty or incorrect air filters. If the air filter gets restricted enough, it causes the engine to suck oil into the turbo inlet from the closed crankcase ventilation system. Eventually enough of it gets pumped through the intake system that the charge air coolers begin to plug up. I wouldn't have believed it if I hadn't worked on a truck that had a plugged cooler. Hino actually has now recommended that only the factory style Donaldson air filters be used. I personally feel they need a bigger air filter in them to begin with as the filters I've changed that caused the oil in the intake didn't even cause the restriction gauge to move into the red, but this is hinos theory.
 
The extended oci's in Europe would have me worried if I was a manufacturer relying on non dealers to service vehicles properly.

As in the US, UK mechanics can be simplistic with assumptions on correct fluids. And if I understand correctly, there are far more oil specs in Europe than in the US.

Conversely, there is very little critical maintenance in warranty periods although I am not as familiar with diesels and turbo maintenance risks.
 
Originally Posted By: TrevorS

I found it because Purolator are claiming a clean air filter can give 11% better acceleration, which turns out to be true in one instance of WOT testing.


Well, if you are going to really accelerate, doing it at WOT is the best method.
grin.gif
 
Originally Posted By: Jim Allen

Emissions on a gas engine wouldn't change either... at least to the point that driveability is grossly effected. I believe that is mentioned in the story as well, if not specifically, then as a side note.


You're thinking fuel injected I'm sure. On a engine with a carburetor, if the filter is very clogged up it can cause it to run very rich. I'm sure you've been behind some old 1972 Cadillac on the highway puking black exhaust smoke before that about made your eyes water because it was running so rich.
cry.gif
 
Originally Posted By: TrevorS
The extended oci's in Europe would have me worried if I was a manufacturer relying on non dealers to service vehicles properly.

As in the US, UK mechanics can be simplistic with assumptions on correct fluids. And if I understand correctly, there are far more oil specs in Europe than in the US.

Conversely, there is very little critical maintenance in warranty periods although I am not as familiar with diesels and turbo maintenance risks.


There are indeed a lot more oil specs in Europe.

But I don't think many mechanics would have a simplistic attitude to the oil specs they need to use.

Castrol products have been badged up as Ford spec, Volvo spec or VAG spec for many years.

But despite all these different specs most oils fall into three or four catagories.

A3/B3, A3/B4, A1/B1 and A5/B5 and more recently C1/2/3/4.

They do tend to overlap somewhat but normally A3/B3 will be Semi Synthetic or mineral and A1/B1 also Semi Synthetic rather than full.

I don't think this is anything to do with better training but purely as a result of the longer OCI common in Europe.


Some of the strictest oil specs are Jaguar Land Rover, they use Ford 934B which is pretty rare, even my nearest Ford dealers don't stock it and I checked three.

There is a lot less choice of oil brands in Europe and also mineral oil is pretty rare. As is part synthetic oil like GTX is labelled in the UK most oils are either semi of full synth.
 
What do you think of Halfords, Triple QX and supermarket brand synthetic oils that meet ACEA specs?

They are sometimes on sale and cheaper than US Walmart pricing. ECP recently had 5 liters of MB229.3 Full Synthetic oil and any filter including fleece filter for less than US$20.
 
Originally Posted By: ZeeOSix
Originally Posted By: Jim Allen

Emissions on a gas engine wouldn't change either... at least to the point that driveability is grossly effected. I believe that is mentioned in the story as well, if not specifically, then as a side note.


You're thinking fuel injected I'm sure. On a engine with a carburetor, if the filter is very clogged up it can cause it to run very rich. I'm sure you've been behind some old 1972 Cadillac on the highway puking black exhaust smoke before that about made your eyes water because it was running so rich.
cry.gif



I was... but the test did include the Q-Jet equipped '72 Pontiac and with a totally plugged air filter, FE only dropped under 3%. Around here, anything that old has long since gone back to the earth or is in a collection somewhere. I haven't been subjected to that scenario for a long while now.. Actually... I kinda miss it. Seeing old cars running around on a daily basis, I mean.
 
Originally Posted By: TrevorS
What do you think of Halfords, Triple QX and supermarket brand synthetic oils that meet ACEA specs?

They are sometimes on sale and cheaper than US Walmart pricing. ECP recently had 5 liters of MB229.3 Full Synthetic oil and any filter including fleece filter for less than US$20.


I have looked at Triple QX, Halfords and also Carlube oils.

Rumour mill says that Halfords is made for them by Castrol but i have no confirmation

I did use Carlube 5w30 C3 oil in the Pathfinder and it the camchain was a little bit noisy on start up so swapped it out after 5k(from memory). Then stuck with the 5k interval since then.

I do actually have the used oil analysis sample in my garage to go to Blackstone.

If it meets the specs then i reckon they will be up to the job.

But i am an oil tart if i'm honest and due to Costco being cheaper for Castrol Edge, Castrol Magnatec and Mobil 1 than Halfords, ECP or German & Swedish are with their own brands it is a no brainer for me.

I did get a decent deal on 10 litres of Shell 5w30 AFL C1 oil. Or good for the UK. £71 for 10 litres. 25% discount.

The fresh Shell oil has reduced the start up hydraulic tappet noise a bit. To be expected with such a big mileage in under 2 yrs.

I have been unable to find any specs of those own brand products.

Will be interesting to see how the Carlube compares to the Castrol Edge when i finally get my used oil analysis done. Going to send a sample of the Jags oil that just came out also.
 
Costco Magnatec on sale seems to be the best deal for a branded oil with known specs esp since some grades are Full Synthetic.

Hard to pass the GBP13 deal on 5L Triple QX Full Synthetic 5w40 plus any filter. That is almost like a Black Friday deal if you need an expensive filter.

Halfords had a GBP10 5L Full Synthetic own brand special a while ago too which is cheaper than Walmart SuperTech Full Synthetic.
 
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