How do you find out how often to change the oil on your car? The maintenance schedule of your owner’s manual. It will help you decided how often to change your oil based on how you drive.
Take note if you drive under normal or severe conditions. Normal Driving Conditions = most trips over 10 miles, driving on the highway/not a lot of stop and go, not dusty conditions. If you have one of the previous mentioned conditions then you are considered driving under severe conditions. Follow the severe driving conditions for changing oil the manual recommends.
There may be a separate book for just maintenance if you cannot find the schedule in your manual. Most newer cars also have a maintenance reminder built into the car and will tell you when an oil change is required (see pic below). This can help you save some money on your car because you will have more time between oil changes.
You should know that if your maintenance schedule says 5,000 miles that means 5,000 miles or LESS, not more. If you tend to live on the edge, like me, and wait until the last minute to do things like get gas, you probably go over your recommended maintenance schedule by 1,000-3,000 miles STOP THAT. Remember what happens to your engine if your are low on oil or if the oil is dirty? Does vagina ring a bell?
Ultimately it is what you feel comfortable with. I have a customer who changes his oil every 3,000 miles even though his owner’s manual says to change the oil every 5,000 miles. It makes him feel better about his car.