Depends on the enviroment too. Where I currently work we have a 2005 Peterbilt roll off truck that has a decent size engine in it considering it's a roll off truck, CAT C13. But it has a dinky under hood air cleaner. Our yard is very dusty in the summer and will clog up a new filter with dirt very quickly to the point that the filter collapses from the engine trying to pull air through it. My truck has dual vortox cleaners and doesn't need servicing nearly as much as the under hood one. However, when we do replace the filters in my truck they are quite expensive. I can't remember for sure but I think they are almost $100 a piece.