Changed out the cabin and air filters on my wife's 17 Nox 2.4 this afternoon. At roughly 32k miles, neither one was that bad, but I had changed the cabin filter once before and the HVAC is usually set to recirculate so that helps I'm sure. The air filter could have easily went to 50K miles, but this vehicle only sees urban and freeway driving, no gravel or dusty roads, so take that into account if your ride does. The airbox had some fine sand and one leaf in the bottom of it, I used a little hand vac to vacuum the sand out. This is an easy DIY job for even a semi-crippled up oldster like myself, a dealer tech may have removed the leaf from the airbox, but I highly doubt they would have taken the time to get the fine sand out. The inlet to the airbox is right behind the passenger side headlight, so I guess you could call it at least a semi-cold air intake, although I've never noticed really high under hood temps on this Nox 2.4 like I did on an 04 Bonneville SLE with the 3800. Used AC-Delco filters, will get to the oil and filter change in the next day or so.