Primarily for safety. When working under the hood, it is a good idea to disconnect the negative lead of the battery to prevent damage to electronic components and yourself.
For example - many vehicles have electric fans that can come on without warning which could lead to loose clothing getting caught or fingers being separated from their hand.
It would also prevent your "helper" from starting the engine or honking the horn while you have your head under the hood.

 

Yea, my helper is 3, he loves the horn "can I honk your horn papa..?"

 

way back when my "helper" was a little squirt, he liked turning the ignition on, usually when i had a spark plug or coil wire in my hand.

it took me quite a few shocking moments to remember to put the keys in my pocket when under the hood.

 

Today, my helper, age 2, showed me at the playground how to drive a car and shift.

 

I'm taking out the K&N that came with my X and putting in a Motorcraft.

It there's one thing I've learned on this site, it's Ford products love Motorcraft filters, and they rate among the best... no fuss no muss and cheap, why buy anything else?

 

because the other guys tell really good lies about how "good" their junk is.

 

If Ford or any manufacturer thought these would up the performance and fuel mileage they would be installed at the factory.

Simple as that.

 

I put one in my E450 Super Duty and one in my F-250 and one in my wife's B150 Ram Van.
All three of my vehicles ran like they were starving for air. I took the Air Cleaner cover off of my wife's Van. It immediately started running better. For some reason the Air Cleaner Canister on my E450 would not close properly and the plastic clamp that held it closed broke(was that an omen ?) any way to make a long story short I took all of the K&N Filters I had and replaced them with Motorcraft on my two Ford Vehicls and I put a Mopar Filter in my wife's Van.

I have to agree with Stuart and I will say it again........if GM or Ford or Mopar thought that the old Oil Bath type Air Filters worked they would still to this day be using them.

Also I am going over to the Dark Side I have ordered a new Truck......I also bought SWMbO (the wife) a new Jeep Grand Cherokee. I would have bought a Ford Bronco for her but we could not wait that long to get her a new vehicle. And I bought a Ram 2500 CC/LB 4x2 6.7L IL6 Cummins Turbo Diesel. ( I was really looking at a Powerstroke, but I have many a mile driving a Semi with a Cummins and also a Cat Diesel Engine in them).
I still have my E450 and plan to keep it for a few more years.

 

I put a K&N cold air intake on my 2011 f250 6.7. I noticed a slight difference in power mainly when towing. After a month I had a check engine light. Took it to the dealer and they cleared it. It was reading different air flows from the MAP and MAS so it threw a CEL. It threw it a second time about 2 months later. Cleared the code via OBDII reader. Other than that no issues. I'll continue running it for now. I've had K&N intakes on both my old 1/2 tons with no issues.

 

plan on replacing the engine on that 6.7 soon, they are the worst i have ever seen about having clean intakes. once the k&n lets enough crap through it is going to spit the turbo into the engine.

 

anyone else had issues? proof?

 

If you think Ford would increase the cost of a single component by 500 to 600% you are not a very smart guy...regardless of the benefit.

 

where would it increase cost? those filters only cost pennies to make. what they sell to the open market for is the problem.

 

You make a good point but the oil / cotton gauze filter has to be more expensive than a paper filter. Any part cost increase is a hard sell for anything mass produced.

 

Going to throw my $.02 in since I have owned K&N. Had an '96 Dodge Ram 1500 5.9 gasser and I put the K&N intake on after adding a flowmaster muffler. The thing sounded SWEET!!! It also had "quicker" throttle response for whatever reason, but it did not gain any power that I could tell or feel. Was religious about cleaning and oiling the filter as per recommendations. I had zero problems, but did notice when pulling to clean there was a slightly dusty film passed the intake, which was correctly mounted and sealed BTW. Did not have that with OEM intake, but it being a gasser and it was only a very tiny particulated film I did not worry about it. Sold the truck in '03 without any issues.

Couple years ago I picked up an '03 6.0L that had a K&N intake and I could not wait to get it out!! Guy that put it on was good about maintenance and I noticed the same type of small dusty film beyond the filter. Having limited, but increasing knowledge of turbo diesels I knew that was bad and did not want to gamble. Especially when turbos and everything beyond into the motor are not cheap!! Also, why is it considered a "cold air intake" when it pulls in engine compartment air? The OEM snorkel exits the front of the truck toward outside air so if you are truly wanting cooler air then that is a better way to go.

Did the K&N look bitchin? Yeah, but I would prefer to be on the safer side of $2-15k. I did like the sound of it when my turbo would spool up though.

In my own opinion I would not go with a K&N anymore for anything. To each his own and whatever may come is what it will be. Just like rebuilt vs reman injectors. Some have problems and some do not, but everyone has their own opinion.