probably now cuz I bet you haven't changed yours in awhile.

Every 4k miles is good enough. If you race your engine like hell all the time try to get your oil changed every 2k miles at least. Or you can be a freak and change it every 1k miles I change mine anywhere between 1k-2k whenever I remember to do it.

 

Depends on useage and what oil you have.A good synthetic in a highway driven car can go up to 10k miles between changes without trouble.A vehicle(like my Frontier) that is driven primarily for city or delivery driving should have it changed much sooner.No longer than 3k miles for conventional and 5k miles for synthetic. Remember that the harder you drive it, the quicker the oil will break down and need changing.