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Since purchasing our preowned Acadia in February I've kept track (with pen and paper) of our fuel economy at each fill up. My wife drives this car 95% of the time. Here are the numbers:

2/25-14.62 mpg
3/6 - 16.23 mpg
3/17- 15.30 mpg
4/5 - 14.73 mpg

On 4/5 I filled up with the mid-grade fuel and on 4/6 I installed a K&N air filter, and this is the result we got:

4/20- 19.25 mpg

I'm not sure if the improved fuel economy is due mainly because of using the better gas or the better air filter, so on the 4/20 fill-up I switched back to 87 octane and will post my results at the next fill-up.[/color][/color][/color]
 

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You might want to run more than a tank through; the ECU is probably still learning the new filter and adjusts the engine management software accordingly. Don't forget to pull the battery cables and force the ECU to do a hard reset, then after driving around for a while, go out on an empty highway and do some 3rd and 4th gear WOT (wide-open throttle) pulls to get the ECU to juggle the addition of airflow into the engine.
 

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Everything I have read, and my experience with the Acadia, would say that going to mid-grade gas should lower your mpg as it increases your performance. (i.e. for towing etc.)

If you continue to get better mpg with the new filter, I would love to know what happens if you go back to regular 87 octane gas.

Keep us posted as I have never believed in the K&N story, but if you get better mpg I might actually be willing to give it a try.
 

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I do not believe in those filters (I keep buying them though) except for the fact you can clean rather than replace. Look at the date of fill ups. Everyone's car is getting better fuel milage because of the temp change of the outside air. The car will adjust to the air, sure you will have more air intake, but unless you change the exhuast too, I dont think there will be that big of a difference unless it will be a cold air intake. You could ice the intake ;D.
 

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Do you really think GM put as many millions of dollars of engineering into this vehicle as they did, and left 4 mpg (25% of vehicle mileage) on the table for want of a better air filter? They would surely spend many times the cost of a K&N for a fraction of that increase. In fact if you go to the K&N site, they don't even claim improved fuel mileage. Their only page on the subject very tactfully says that a clogged filter will cost you mileage. The only real possible advantage of a higher flow system (such as K&N claims to be) is at the very high flow rates (higher HP level) where of course mileage goes out the window anyway and in fact you might find your vehicle able to burn more, rather than less, fuel.
 

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I have used the K&N air filter system for many years. If you stay out of the throttle, you will see marginally better fuel mileage (1.5 to 2.0 mpg has been my experience). I have had no problems of any sort while using this product.

With that being said, when most people install a K&N, they are doing it for performance reasons. Being easy on the throttle is not what they had in mind. These filters require maintenance that the everyday consumer is not willing to perform, that is cleaning and re-oiling. After a period of neglect, there is a high probability of engine damage. I feel that this is the reason that auto manufactures do not use this type of filter -- more consumer satisfaction issues. These filters do not muffle air intake noise as well as a stock paper filter. The car companies spend a lot of money to reduce intake noise, many times at the expense of performance.

In the end, it's all a matter of balancing all of the above variables at a price that is acceptable to both the company and the buying public. Just my opinion.
 

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xseler said:
I have used the K&N air filter system for many years. If you stay out of the throttle, you will see marginally better fuel mileage (1.5 to 2.0 mpg has been my experience). I have had no problems of any sort while using this product.

With that being said, when most people install a K&N, they are doing it for performance reasons. Being easy on the throttle is not what they had in mind. These filters require maintenance that the everyday consumer is not willing to perform, that is cleaning and re-oiling. After a period of neglect, there is a high probability of engine damage. I feel that this is the reason that auto manufactures do not use this type of filter -- more consumer satisfaction issues. These filters do not muffle air intake noise as well as a stock paper filter. The car companies spend a lot of money to reduce intake noise, many times at the expense of performance.

In the end, it's all a matter of balancing all of the above variables at a price that is acceptable to both the company and the buying public. Just my opinion.
Exactly.

My 100% city mpg went up with 89 octane but for whatever reason my hwy trip 89 octane wasn't quite as good. It may be because I was pushing it more since it felt ever so slightly peppier. :-\
 

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The K&N's also seem to be a little noisier than a stock filter, which I'm sure GM wouldn't want.
 

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A cheap pleated paper filter flows plenty of air. I have had good luck installing cold air induction kits that improve performance and possibly mileage, at the expense of a lot of engine noise that the manufacturers would not tolerate. These systems work because of larger, free flowing filters and duct work, and more fresh cool air, not merely because of the filter material.

The biggest factor in mileage is your right foot. Put some magnets on your fuel line and then drive really gentle to see if the mileage goes up.... guess what, it will!
 

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Unless you install a CAI set-up, you will not see any better mpg with oil replacement type filter. Save your money!
 

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For the most part GM vehicles have two tables for timing in the ECM/PCM, a low octane and a high octane table. In addition there are other parameters in the computer that pull/advance timing based on many variables. The net is that if you run higher octane and/or other conditions are right and GM did indeed populate the table the engine will run more efficiently and get better fuel economy. I've seen this on my Silverado, Avalanche and on our 2007 Acadia. Could the air filter help, maybe some but a gain like that.....not likely. In the next couple weeks I'm going to have my computer tune looked at to see what is going on to see what indeed GM did with the Acadia.

All too often I've also seen people change driving habits after doing a modification to their vehicle which again will have a significant effect on mileage.
 

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Where did you get the K&N filter from? Both local places that I found had a part # for it.. but didn't have availability yet.

I thought about trying to fabricate a cold air intake for the Acadia.. but won't know any more till I take the current airbox and plumbing out to see what all would be entailed. Might just go w/ a short ram intake w/ a cone filter... and maybe some sort of heat shield.
 

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There is a tube that goes vertically down from the air filter box. If you could extend it horizontally to the front bumper area, I would think that you would get a ram air effect at freeway speeds. I was able to order mine through my local auto parts store (Kragen).
 

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In making your own CAI, I would be concerned with the MAF and crack case breather. The computer will probably adjust to 10% more air intake before the engine light comes on and stays on. Your engine will be running to lean and then pooof!!
 

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I just installed a k&n a couple days ago. But forgot to reset ecu, can this adjust/learn engine management?.. Am sure it needs to be flashed.
 

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Disconnect battery for about 3-5 min.
 

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So back from vacation which was about 320+miles away, and our avg mpg was jumping between 22.8mpg-23.1mpg on 87 gas. :p :sleepy:
 

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One thing to keep in mind with K&N filters. While they do flow more air they also flow more dirt.
 
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