The recommended mileage for changing oil in a car is between 3,000 miles to 5,000 miles.
However some vehicles can go 10,000 miles between oil changes but it depends on how often you drive your vehicle.
I have a truck that can go a few years between oil changes because it's not driven that often but my car that gets driven more needs an oil change once every year.
I usually have 10,000 to 12,000 miles on my car every year so it gets an oil change at least once per year and I use synthetic motor oil that can go longer.
I also change the oil filter along with the engine oil.
If I notice the oil getting darker on the oil dipstick when checking the oil then I change it.
But usually you should change the engine oil every 3,000 to 5,000 miles for conventional oil which could be every 6 months depending on how often you drive the vehicle.