On May 10 I installed a K&N filter in my '05 FEH. I have recorded before and after mileage as measured at the pump, and thought I would share it with you.

The short version is, before the filter I got 32.7 mpg over 1876 miles. After the filter I got 34.8 mpg over 2086 miles.

Assuming I haven't made some funny error when running my numbers, replacing the paper filter with the K&N has given me an improvement of 2.1 mpg.

The only source of error that I can think of is that it has been warming up. I purposely limited my sample window to limit this effect. My first tank before the filter was filled on 4/3/07, and the last tank after the filter was filled on 6/5/07.

I haven't particularly noticed more power, but that's not why I tried this in the first place.

Enjoy,

salsbr

The long version is this.

Before filter:

415 miles, 13.219 gal, 31.4 mpg
424 miles, 13.117 gal, 32.3 mpg
395 miles, 11.747 gal, 33.6 mpg
339 miles, 9.853 gal, 34.4 mpg
303 miles, 9.399 gal, 32.2 mpg
TOTALS
1876 miles, 57.335 gal, 32.7 mpg

After filter:

154 miles, 4.298 gal, 35.8 mpg
259 miles, 7.264 gal, 35.6 mpg
400 miles, 12.485 gal, 32.0 mpg
291 miles, 8.728 gal, 33.3 mpg
490 miles, 13.925 gal, 35.2 mpg
492 miles, 13.187 gal, 37.3 mpg
TOTALS
2086 miles, 59.887 gal, 34.8 mpg

2005 Ford Escape Hybrid - Titanium Green, 4WD, Appearance Pkg, Leather, Nav System

I noticed pretty much the same thing.
However, I have no way to prove if it was from switching from paper to K&N, or from switching from dirty to clean! ( I had 25k on the stock paper one )

I guess you could buy a clean paper one and see if your mileage drops.
-John

Oh yes, I forgot to mention that. My previous filter had been changed around the time I started keeping numbers. So, the filter was new. I have it in my garage, and it's still quite clean.

But, good point.

2005 Ford Escape Hybrid - Titanium Green, 4WD, Appearance Pkg, Leather, Nav System

Oh, and one other thing. I have been exclusively using Shell gasoline.

2005 Ford Escape Hybrid - Titanium Green, 4WD, Appearance Pkg, Leather, Nav System

The car I traded in for the TCH last month jumped ~2 mpg when summer blend arrived.

Not sure which KN filter you're using but there've been reports of some of them passing much more contamination through to the engine, showing up as high silica readings in used oil analysis.

I wonder why Ford engineering sacraficed 2 mpg for a restrictive air filter. Did thye recognize the 2 mpg change between the selected air filter and a less restrictive air filter?

2008 FWD Escape Hybrid

Automaufacturers don't like reusable air filters. They beleive if they are oiled incorrectly they could cause damage, they believe it allow more particulates into the engine, and it replaces a part they can make money on with replacements with one that lasts for the life of the vehicle.

In their minds the risk/benefit/monetary equation comes out in favor of the paper filter they selected.

There are other types of high flow filters. The simplest way is to increase the filter media (paper) of the filter. More pleats or a larger filter!

2008 FWD Escape Hybrid

Did you know that the only time less restrictive airflow will be advantageous is at WOT and at or near the engine RPM for PEAK intake airflow. Otherwise the throttle butterfly valve is the primary restriction to intake airflow.

Sounds as if you go WOT and wrap that engine up to the top end fairly often.

Ah... thats what you were asking!