i put a 14x3 K&N on last week, with a 3 inch PVC pipe ( the OEM pipes are 4 ) and went from ~16 to 18.5

put the stock box back on, and went straight to ~16.

even drilled 2 holes in the front of the box, (you can see them from in front of the truck - cheapo "ram air"). no joy.

pulled the gauze pre-filter off the OEM filter tonite, showed high 19 and 20.

with 6000 miles on it, could it be that dirty? it was gray, not quite black.

 

I'm making an assumption that you are looking at the overhead computer?

I don't think that would make a 2 mpg difference at all. That's not to say that it wouldn't...it just wouldn't happen to me.

Figure it out by hand, drive it the same way (as close as you can) for a tank apiece and report it to us goofballs.

 

ok, will do
i thought the overhead console is almost right on, with a stock truck?
here's a cut &paste of my excel spreadsheet, showing the K&N rig i had on it.
it matched the overhead dead on.

will reportback...


Miles on truck Trip Odometer Gallons Mileage Cost
costs so far Cost per Gallon Cost per Mile type Driving

2915 308.5 19.083 16.17 $27.27 1.43 0.09
fill up before trip - city
3315 399.8 26.293 15.21 $40.20 1.53 0.10
fill up in Shelby, both city & Hwy
3681 365.7 20.225 18.08 $30.36 1.50 0.08
in Columbia - all highway - unloaded
4133 452.1 27.621 16.37 $40.30 1.46 0.09
end of hiway, round town
4379 -- $42.61 -- -- oil change
4458 324.6 19.549 16.60 $29.30 1.50 0.09
around town - after first tow
-- -- -- kid filled up
5364 484 28.161 17.19 $41.65 1.48 0.09
6758 519.3 28.609 18.15 -$44.60 -1.56 -0.09
little K&N rig

 

I get the same fuel mileage now (41k) as I did new. Mine came with an air filter with no prefilter, and now I have one with a prefilter. I do have a 4" hole in the bottom of the air box. Same interstates, same time of year. FWIW