Stock air filter is restrictive and robs hp, but it does a good job of catching everything but the very finest kind of dust. This passes through and makes it into your oil, but is not stopped by your oil filter (way way smaller than 10 microns which is all the oil filter says it will always stop)
Now these stock air filters do get plugged up and require a reverse blow out with an air gun every 6 months. Eventually they get plugged up and then they cost you like $39.00 dollars to replace now-a-days.
K&N makes a 1/4" thick thin oiled cotton mesh trapped inside screening sort of folded filter that fits in the same space for $49.00 that requires cleaning and re-oiling every six months or so. Oiled filters work better, but a 1/4" filter has very little carrying capacity so they get dry and start to pass all sorts of stuff, being only 1/4" thick and really really dependent on that oil to work correctly.
Oiled media filters have a better chance of catching really fine dust than any other sort of filter media, so I made myself up one with a 2" thick compressed poly-fiber mesh which is coated in thick oil which can run for like 2 years before requiring attention and even then it only gets dirty less than half way through the thickness.
This gives me improved air filtration and is still low air resistance compared to a stock filter. Here is the tech tread.
http://suzukisavage.com/cgi-bin/YaBB.pl?board=tech;action=display;num=1183640744Improved oil filtration requires you to remove sub micron sized ferrous wear particles to keep them from recirculating in the oil. Oil filters that can do this fine sub-micron job are expensive and they plug up fairly quickly. So I went a different way to achieve the same goal. Here is that tech thread.
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1197231468===============
Based on these improvements in very fine dust air filtration and super fine oil ferrous particle trapping I have no issues with running T-6 from one year to the next on my bike.
I still can't stomach going any longer than a calender year, I jest can't bring myself to do it. I know I can, I just really don't want to.