I recently put a K&N drop in air filer on my 5.4l. My records of fuel consumption ever since that event indicate a loss of economy by about 1 - 3 mpg. Is this an air intake problem or a computer problem? If it is a computer problem how is the computer reset to see a change in the air intake system? No other changes have been made.

 

Disconnect your battery (truck off of course) to reset the computer.

 

Whats being reset in the computer, this is something I plan to change in my unit. Just the insert filter d/t our cold winters.

 

When you "reset" the computer, you are returning it to factory settings. The computer in your truck "learns" and adapts to your driving styles/habits/conditions to better optimize the engine's efficiency.
Sometimes, when a new mod is installed, the computer(PCM) can adapt to the new mod quicker if it is reset and begins the learning process from scratch.

 

Moragin,

with the weather changing from cold to colder you will get a loss in fuel economy. I have experienced 15 mpg in summer, and 13 in winter, with fall and spring about 14. This is normal because of the engergy to move cold oil and grease. The difference in fuel economy from your K&N is barely noticable. When I had two trucks I moved the K&N from one truck to the other and did not notice a difference in either truck.

I seem to recall some removing the K&N in the winter only, but don't remember why or where I read that. It may have something to do with the design and ice taking away its effectiveness.

I could be wrong, but just can't imagine resetting the computer for a K&N because the daily change in pressure and tempature would be more impacting than the change in air flow an air filter makes.

If you have a 4x4 and run it in 4H you see another 3 mpg drop. I've followed the advise here and on BITOG and I'm running about 1 MPG more than the same time last year. I'm still at 15 and it was 28* this morning. Point being that maintaing the same milage is actually in increase for my truck.

 

The reason for less fuel economy in the winter is the fuel formulas are different in the winter. All the gasoline companies have warm weather formulas and cold weather formulas. The summer fuel has a higher BTU content than the winter formulas, therefore, you get more mpg in the summer.

As far as cold oil and grease, the lubricants are warmed up to normal operating temps in just a few moments of driving and are not a significant factor in cold weather fuel economy.

All other factors remaining the same, I have been getting 1 mpg less in the last month or so due to the change to winter fuel formulas.