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K&N Air Filter...anybody get worse

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gas mileage with it?


Recently on my 05 Grand Caravan (work/space vehicle)

I switched to

1. Fully Synthetic Mobil One oil

2. K & N air filter.


And on it's first tank of gas I got an average of 17.6 mpg!!


I had been averaging around 20.5 in mixed driving.

Prior to the 17.6 mpg tank, my worse was like 18.9 my

best was like 22 ish.

On an all freeway trip driving 80-85 mph with me and

an additional 400 pounds in the van, I got 23.7 mpg


EPA is 19/26


I don't think I drove any different on this last tank than I have

since I got the van. The only change was the synthetic oil and

the K & N filter.

The oil shouldnt affect it one bit, and have used synthetic in

other cars with no gas mileage penalty.

I've used a K&N in most all my cars in the last

8 or so years, and in my 98 Corolla I felt I got worse

gas mileage as well after putting the K&N in so I took it

out and put the stock back in.


So I'm curious...does the increased air flow have a negative

drawback on some cars. Is the car's ECU compensating for

the Air/Fuel ratio that has changed and pumping more gas in?

I'm going to give it one more tank full.

I'm actually kind of "babying" the driving now to see how good I can

get, but if I don't get AT LEAST 19.5 mpg on this tank full of mixed

driving, I'm going back to the stock filter, where again I averaged

about 20.5-21 mpg in mixed driving on several different tanks of gas.

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Increased flow should improve performance and gas mileage assuming you don't get any weird ECU phenomena like you're describing.


But I read an article awhile back where some guy compared a few different air filters. He found that a brand new paper air filter will flow better than a K&N filter. The main advantage K&N had is its durability, filtering & flow capabilities over a longer period of time basically outliving what a paper filter can do. Anyway, if you replaced your stock filter right away you may not have necessarily improved airflow. I'll see if I can find that article...


I found it:



I'd think the difference in airflow should be negligible in terms of gas mileage, however.

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Something else is going one. Both changes you made should have improved mileage, albeit insignifigantly. The drop you experienced is very signifigant. I'd go at least one more tank to see if it changes. If not, you might want to look into other maintenance issues.
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Actually, increased airflow must be compensated with increas fuel flow to keep the mixture the same. So it should increase fuel consumption a bit, but not that much!


Perhaps the oil in your K&N fouled a sensor? There has been many reports of that. K&N are basically not worth the trouble...

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  • 2 weeks later...

Well, after another low MPG tank in my 05 Grand Caravan, I

decided to try to figure out what the cause of my nearly

2.0 mpg drop in fuel mileage was.


About 800 or so miles ago, I decided to change the horrible rated

Goodyear Integrity tires on the van, to a MUCH higher rated tire in

the same category.

After finding out the stock Goodyears weighed 22 pounds each, I wanted

to find a high rated tire of the same weight.

I found the lightest, yet highest rated tire was the Firestone Affinity LH-30

listed by Firestone, on their own website as 22 pounds.


So it got me thinking, could they have lied!

Took the tire/wheel off and weighed it on my scale.

And lo and behold...the Firestone tire weighs 26 pounds!!

4 pounds heavier than FIRESTONE CLAIMS, and 4 pounds heavier

than the stock Goodyears!!


I was ticked!!


There was the problem.

4 additional pounds of rotational mass sucked up an average of

2.0 mpg on my work van over three tanks of gas and 800+ miles

of mixed driving!!


Perfect support of what additioal rotational mass does to performance.


Needless to say, I'm writing a scathing letter to Firestone, and my buddy

Bart at America's Tire store is going to allow me to swap the tires out

for another brand.


Another note, before getting these tires (a month or so ago), Tirerack did not list tire weights for the majority of their tires. Checking again yesterday, and they

have the weights of basically EVERY tire! A nice new touch I've been wanting

for years.

They list the weight of the Firestones at 26 pounds...just what my scale said!

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So I also drive a mechanical Monster Chevrolet Venture 3.4 sfi V6 in the rest of the day. On the highway I will get 22-27 mpg depending on the speed. I will never forget actually getting 27 creeping from Indianapolis one night in miserable rain and poor visibility. I guess it was the 50ish mph speed that did the trick. Highway speeds of 75 will get me 23-24. But mind you...I have the filter (K&N) and a real air intake on it. My overall impression is that I did sacrifice 1-2 mpg at the expense of added power (I will race your 3.8 L Dodge Caravan any minute of any hour of any day...or any other 3.5 ish - 4L engined SUV or minivan) but I have not been able to prove it mathematically.


I have had the filter, intake since September 2002.

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