Sure it can - however as you stated it has a lot to do with your driving characteristics. If you go out and romp on the gas because you like the increased power it has given you or you like the sound than fuel mileage will be all relative.
The stock paper air filter will offer the best protection for your engine, meaning it will filter the incoming air the best. Although that creates a pretty bad restriction....
An after market oiled or non-oiled air filter will dramatically increase the air flow and EFFICIENCY of the engine allowing it to breathe easier.
Depending on what filter you choose has a lot to do with how much protection you still have as well as increased flow. I noticed that you have a k&n filter in your signature - great filter although a standard k&n only offers about 4 layers of cotton & gauze. This equals great flow, although not that great of protection.
Other top brands offer more layers, oiled and non-oiled versions etc... I for instance run an airaid filter which is very similar to a k&n and uses multiple layers of oiled cotton & gauze, however they then incorporate an additional layer of protection called synthaflow which allows for improved filtration over a standard cotton & gauze filter without harming airflow. I have heard that airaid also just released a new non-oiled filter, however I am not familiar with it.
As long as you check your filter at regular intervals you should be just fine running the k&n - if you do use it under severe conditions than you might want to service it more often. With that being said however keep in mind every time you service a cotton & gauze air filter you take away a little bit of the media during the process.
Cleaning your air filter at every oil change is overkill.
I don't mean to sound bias and I'm not bashing on k&n, just telling you what I have learned about after market air filters and cold air intakes.
I was told a long time ago to think of an engine as a giant air pump - the more air you can get into it and out of it (exhaust) more efficiently, the more efficient it is going to be overall.
Hope this helps!
