2002 Nissan Altima 2.5L 4 cyl Los Angeles -- temps vary from 40-110 degrees I don't put a lot of miles on my car and only drive it maybe 3-5x a week, in mixed driving (mostly city-- this is LA, CA). I'm driving about 3-4K miles per year. I recently put in Mobil 1 synthetic 5w-30 (viscosity as per owner's manual). How often should I change my oil? Is once a year sufficient, or should I do 2x/yr?