A study on effects of dirty air filter on mpg

[Yury]

In case this hasn't been posted yet.

A dirty air filter is commonly seen as a significant factor in fuel economy.
I find this questionable in fuel injected cars that vary the injector pulse based on the lambda sensor reading, i.e. maintaining a complete (i.e. effective) burn regardless of the variations in the air flow).
Some say that increased pumping losses are a factor, but it all remains anecdotal until someone actually tests it.

This is exactly what it is, a study. It's a long read, and I have not completed it myself, but it is interesting.

http://www.fueleconomy.gov/feg/pdfs/...02_26_2009.pdf