hi there, about your question, in the dealer they change the filter everytime they make the service, but im pretty shure 20000 km in a paper filter is the max you cant get, if you dont drive in a dusti condisions. if you buy a k&n drop in filter or cai you can clean it every 10,000 miles, and for 38 a paper filter is better to buy a drop in if you dont want to expende in the cai, thats what i do. In mi olds man truck, the air filter changes every 10,000km because the dust in here, and the dealer charge 600 pesos (46usd) and i can get a drop in at autozone for the same. Check how dirty is. is the easy way.