I just recently bought my first Xterra. It's a 2002 and I love it! BUT - I commute 100 miles to attend classes and once I drive it about 50 miles, an odd grease smell permeates the interior only. When I park it, I can't smell it outside of the vehicle. It gets worse the longer I drive it and it's driving me crazy! I changed the cabin filters (they were filthy - I doubt they had ever been changed) and that didn't work. I checked the carpets, under the seats, etc., and can't find anything. Any suggestions?