You must never drive in dust. All K&N's do is filter out the bugs and grass clippings. If you stay on the asphalt all the time, then you don't even need a filter.

 

Sure a turbo diesel motor the K&N is a no-no - especially when off-roadin'. A normally aspirated motor (diesel or gas) it's fine. The case is made with the older 6.9L we used, but especially with my Mustang. Used to drive it on Soggy Dry Lake Bed in Johnson Valley CA. It would get caked form the silt, but nothing found it's way into the induction. After 20 years the Mustang still runs without hiccup and isn't smoking (though it leaks oil, coolant, and a bit of fuel around a fuel injector seal). I also use a K&N on my quad...no issues.