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Discussion Starter · #1 ·
I recently installed a K&N 63 Series Cold Air Intake in my 2009 4.8L Silverado. At first it was great. It really woke my engine up and i could definitely feel the small power boost. After putting two full tanks of gas through it though i noticed that my gas mileage plummeted. Before the install i usual got around 380 to the tank and now i am getting no more then 350. To me this is ridiculous. Before the questions start coming in i will tell you that yes i did install the intake correctly and by the instructions with the negative battery cable unhooked.

I just want to know if anybody else has had this problem and if this is in fact normal. Also are there any solutions to the problem?

I would appreciate any help/advice
 

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Well you installed a KN CAI, more air means more gas to get the mixture right, you may want to clean your TB, But usually factory setup is best for MPG. Also how are you testing this ? Resetting the trip meter when you fill up? Also blends of gas can cause bad MPG, being its starting to get cold you maybe working with differnt gas.

Do you have a tune or did the PO have a tune?
 

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justinmo18 said:
I recently installed a K&N 63 Series Cold Air Intake in my 2009 4.8L Silverado. At first it was great. It really woke my engine up and i could definitely feel the small power boost. After putting two full tanks of gas through it though i noticed that my gas mileage plummeted. Before the install i usual got around 380 to the tank and now i am getting no more then 350. To me this is ridiculous. Before the questions start coming in i will tell you that yes i did install the intake correctly and by the instructions with the negative battery cable unhooked.

I just want to know if anybody else has had this problem and if this is in fact normal. Also are there any solutions to the problem?

I would appreciate any help/advice
There's your answer. I can almost promise you the difference in mileage is due to you driving a little more spirited. We all do it after a new CAI or exhaust. We like the sound.... we like the feel...
 

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Discussion Starter · #5 ·
On the first tank yes ill admit i drove with a lead foot but on the second tank i babied it just to see what my mileage would be and still got no more then 350 to the tank
 

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robfriedenberger said:
Well you installed a KN CAI, more air means more gas to get the mixture right, you may want to clean your TB, But usually factory setup is best for MPG. Also how are you testing this ? Resetting the trip meter when you fill up? Also blends of gas can cause bad MPG, being its starting to get cold you maybe working with differnt gas.

Do you have a tune or did the PO have a tune?
I searched K&N's FAQ's and Question Number 1 was "How will a K&N filter affect my vehicle's fuel economy?":

K&N's Answer: 1. How will a K&N filter affect my vehicle's fuel economy?

There is a relationship between air filter restriction and mileage. The theory behind this is simple, the harder an engine has to work to suck air through the intake tubes and air filter, the more gas gets wasted in the process. Many K&N users report an increase in their fuel economy after beginning to use our air filters, as noted on our testimonial page. However, these experiences do not mean you will also experience a change in your mileage. We certainly understand why it is theoretically possible for a consumer to experience a mileage increase after installing a K&N air filter or intake system, however, we do not go so far as to make a general claim that our air filters and intake systems will provide an increase in mileage.

It is virtually impossible to make sweeping and general claims about mileage. Even the EPA fuel rating numbers for new cars are often not representative of the mileage you actually experience. There are many variables that affect mileage such as: tire inflation, the type of fuel, weather, elevation, the speed at which you drive, the gear in which you drive, the speed with which you accelerate, engine maintenance, excessive idling, cruise control, the grade of motor oil you use, and of course, the condition of your air filter. In short, mileage is complicated.

K&N filters are less restrictive than disposable paper or synthetic air filters and K&N Intake Systems are less restrictive than the factory installed air path. So K&N filter technology could be an important tool, when combined with other elements, to help keep mileage as high as possible.

Oh yeah, there's one more limitation imposed by science. If you take advantage of added power by driving more aggressively, you will reduce mileage. You cannot have your cake and eat it too.

http://www.knfilters.com/faq.htm#1

Hope this was helpful! If not, I recommend calling K&N directly and see what answer they supply you with.

Good luck!

Tom
AutoAnything
 

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Discussion Starter · #7 ·
I had read that Q&A before i posted. A little bit of decrease in fuel economy i would be ok with i just did not expect it to dropped by 30 miles to the tank. I am going to clean the TB and the MAF Sensor and see what it does. Hopefully that does the trick. Otherwise i might just go back to stock. Ill post the results.

Thanks again for all the help you guys
 

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I got one on my truck and have not seen a drop like that. Hope things get worked out for ya.
 

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If you just completed the install give it a minute for the truck to learn you. Once that happens you can feel free to put your foot in it to keep the next few fill up at 350. Seriously though it's like everybody said earlier, there's too many variables for you to measure. I have a tuned Beetle and I swear I'm only 18 mpg's :lol:
 

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What size is your tank? If its 20 gal, the difference between 380 and 350 from one tank is 1.5 MPG average decrease. That's really not a whole lot especially when looking at all the variables. Also, not that mileage isn't important, but I sure hope you didn't buy a V8 truck for the fuel consumption!
 

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Discussion Starter · #12 ·
No I definitely did not by a V8 for the fuel economy but losing 30 to the tank is still rough. I have a 24 gallon tank. Yes, I have MAF sensor cleaner. I would not use Throttle body cleaner on my MAF if that's what you were thinking.
 

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Discussion Starter · #13 ·
Update:

A couple days after my first post i called K&N and they told me that they have a few calls about my same problem and they said that they were going to send me out a modified tube which should fix the problem. I installed it today and along with the install i removed the throttle body and MAF sensor and cleaned both of them. I ran out of MAF sensor cleaner so i cleaned it with the throttle body spray which i have done in the past. Everything is back to normal now except for a slight high throttle problem. Heres what the problem is

It turns over just fine and idles fine at the start. After driving for a bit and putting back in to park it high throttles up to 2000-2300 RPMs. It acts like i am accelerating. However it will only do this for like 10 seconds and then go back to a normal idle at around 600 RPM's. Everything else in the truck is fine. Acceleration, deceleration, etc... its all fine.

Im looking for any input on what it could be. Do you think i damaged my MAF sensor from the TB cleaner?
 
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