I have a f150 4.2L. I installed a drop in k&n filter it was easy to do I noticed some improvment in power but in gas mileage none.After a 810 mile trip I got 20.5 mpg the same that i got on the same trip last year.Should there be any improvment in mileage or do i have to install a cold air intake???????

 

I would not expect any improvement in gas milage just with a filter change. It will take a combination of several thing like a better free flow exhaust and a computer chip upgrade to show anything at all.

 

Yeah, a K&N air filter alone will not give you any drastic gas mileage improvements. I wouldn't be complaining about 20.5 mpg, that is great gas mileage for a truck.

 

Just a Quick update the 20.5 was highway in the city I get 15.5.The truck has 3:55 rear 255/70/16 michline tires.Ill look into a better exhasust and chip replacement

 

if u want to watch it go down put 33" bf atko's on.. haha i have the 5.4 with superchip, true dual and volant, and still only get about 16 highway. so i wouldnt change ur truck its already as good as it gets

 

It is just a good investment for a number of reasons. One being you never have to buy another also warranty issues resolved quick. I put mine in a few months after buying the truck so it's hard to say if any mpg's were gained probably. I would say that the money saved on buying paper filters all the time goes toward gas.

 

It just proves my theroy that the filter ad is bogus as they claim more power and better mileage by just droping one in as you proved that you don't get that.

 

Yes, their claims of added horsepower hanks to a drop-in are bogus, but that's not to say there isn't a cost savings there. Sure, the filter costs $50, and the recharge kit another $10. Even if you recharge it every 15,000 miles, the recharge kit is good for 5-10 cleanings. So.... Figure on cleaning the filter 5 times in 75,000 miles cost you $60. If you can find replacement paper filters for $15 each (yeah, right!!) $60 only gets you four of them. If you include the original factory filter as the 5th, 75,000 miles becomes the break-even point for a K&N drop-in. After you clean it the 6th time, you're saving money. $10 every 150,000 miles thereafter for a recharge kit seems pretty reasonable to me.

From the power perspective, replacing the filter will only improve the power if the existing filter was a restriction to begin with.

-Joe