Does a dirty air filter equal oil consumption?

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I have found a few vehicle maintenance web pages that claim a dirty air filter can cause oil consumption to increase. This seems rather unlikely to me. The theory is that a dirty air filter, will at times, creates a relative vacuum in the cylinder pulling oil up past the rings. Wouldn't simply backing off the throttle create the same conditions regardless of the air filter condition? Is there any truth to this? Has anyone experienced this?
 
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You're right- on a modern engine a dirty air filter is pretty much exactly the same as keeping the throttle partly closed. Except for one thing: PCV make-up air is often drawn in between the air filter and throttle body. If the air filter is very restrictive, oil mist could get sucked through the PCV make-up air plumbing and into the intake tract, especially if the engine doesn't have good baffles to block the mist from entering that tube in the valve cover or wherever it connects to the crankcase.
 

WobblyElvis

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Very interesting...... The oil consumption in my car has increased a little over the past two years and the air filter is very old. It may have as much as 70,000 miles on it. I am about to change it and I'll try to notice if the oil consumption goes down.
 
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Originally Posted By: WobblyElvis
Very interesting...... The oil consumption in my car has increased a little over the past two years and the air filter is very old. It may have as much as 70,000 miles on it. I am about to change it and I'll try to notice if the oil consumption goes down.
WHy would you leave it in that long?
 

WobblyElvis

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Performance does not seem to have suffered. I bought the car used and have put 53,000 miles on it and haven't even looked at it. I'm guessing at 70,000 miles, it could be more. I'm cheap and lazy, don't tell the wife.
 
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dirty air filter shouldn't be restrictive enough to cause elevated vacuum on Normally Aspirated engine (at least elevated vacuum enough to cause additional oil draw from the engine part). While some might say that the elevated oil mist day may occur from the PCV side, or oil drawn from the valve stem seal side or even oil control ring side, my take is that if the elevated vacuum imposed by a restrictive air filter is so great to the point of causing elevated oil burning, then most likely (a) your engine isn't running properly to begin with, due to such highly restrictive air filter (not enough air coming through) and/or (b) your engine is excessively worn enough to burn oil anyways, regardless of the condition of your air filter. Q.
 
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Originally Posted By: WobblyElvis
I have found a few vehicle maintenance web pages that claim a dirty air filter can cause oil consumption to increase. This seems rather unlikely to me. The theory is that a dirty air filter, will at times, creates a relative vacuum in the cylinder pulling oil up past the rings. Wouldn't simply backing off the throttle create the same conditions regardless of the air filter condition? Is there any truth to this? Has anyone experienced this?
Not likely. Sounds like theory overriding practice. I agree with your take on it. Wayne
 

CT8

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Originally Posted By: WobblyElvis
Performance does not seem to have suffered. I bought the car used and have put 53,000 miles on it and haven't even looked at it. I'm guessing at 70,000 miles, it could be more. I'm cheap and lazy, don't tell the wife.
Don't say cheap say thrifty.
 
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If there's too much vacuum the PCV valve will close, blocking most if not all of the flow. That's why it's not a constant orifice, usually. If there's too little vacuum any blowby goes out the vent tube anyway. A more closed throttle causes vacuum just like a dirty air filter. Just doesn't make sense.
 
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Originally Posted By: CT8
Originally Posted By: WobblyElvis
Performance does not seem to have suffered. I bought the car used and have put 53,000 miles on it and haven't even looked at it. I'm guessing at 70,000 miles, it could be more. I'm cheap and lazy, don't tell the wife.
Don't say cheap say thrifty.
even better, frugal!
 
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I used to live a rural area and once found a nest in my air filter. I took a piece of leftover hardware cloth and formed it around the air intake. Still there and no more nests. Cheap enough, took a minute or so, mostly to find the piece to use.
 

WobblyElvis

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I changed the air filter and I've included some pics. The filter had a date stamp of Dec 09 on it so I guess it's at least 72,000 miles old. Looks good for the mileage if you ask me. I did find the PCV tube from the valve cover to the intake was a little wet with oil where it connected to the intake plenum just up stream of the throttle body. Secondly the throttle body had some wet dark black oily/greasy/paste built up on the inside of the bore. I wiped it off with a paper towel and I'll keep an eye on it.
 
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Originally Posted By: eljefino
If there's too much vacuum the PCV valve will close, blocking most if not all of the flow. That's why it's not a constant orifice, usually. If there's too little vacuum any blowby goes out the vent tube anyway. A more closed throttle causes vacuum just like a dirty air filter. Just doesn't make sense.
Can't speak to other OEM engines, but many GM engines now only have a permanent port at the rear of the left valve cover. There is no PCV valve as in the past.
 
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Modern engines' computers compensate for MINOR air restriction from a dirty oil filter, such as yours pictured here, with little if any reduction in performance or MPG.
 
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That filter looks good to me. Could go further if the gasket is OK. Make sure the PCV valve is getting suction. Get some throttle body cleaner spray and clean it proper.
 
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Change it!! you can see all that black micro dust clogging the pleats, I do annual filter changes, dusty in cent Cal.
 

WobblyElvis

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A little more info here. I have examined the air filter closely and believe it is very much plugged. It may not look so bad in the pics but with a magnifying glass, not so good. The surrounding gasket was going brittle as well. You have to consider it has 72,000 miles or more on it, so it's done. I found the vent line, from valve cover to intake plenum, draws clean air from the plenum into the engine while running [idle]. The engine does not have a PCV valve. There is a small passage in the head connecting the interior of the engine to the intake runners for cylinders 2 and 3. It appears under low throttle air flows from the clean side of the air filter thru the engine and to parts of the intake manifold [ I have verified this]. When considerable throttle is applied things change. Manifold pressure would drop and a partial vacuum could be applied to the PVC vent line [plenum to valve cover]. If the air filter were plugged, I would assume considerable vacuum could be applied to the engine internals and maybe draw some oil into plenum upstream of the throttle body. For this to happen I would think there would have to be a fair amount of blow by, but I don't really know. Time will tell as I have replaced the air filter and I will monitor the oil level and look for gunk on the walls of the throttle body. 06 GM 2.2 ecotec naturally aspirated engine
 
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Originally Posted By: WobblyElvis
Very interesting......The oil consumption in my car has increased a little over the past two years and the air filter is very old. It may have as much as 70,000 miles on it. I am about to change it and I'll try to notice if the oil consumption goes down.
70,000 miles on an air filter?!!? shocked2 Seriously? shocked2
 
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