How often should engine oil be changed?

Do you drive frequently? If not, you can change the engine oil every six months or so.

I'm also planning to change the engine oil. Which brand is better?

I personally change the engine oil every 3,000 to 5,000 miles (or approximately every 3 to 6 months). You can take this as a reference. Of course, you might also want to check the owner's manual of your vehicle. Manufacturers usually provide specific guidelines tailored to the engine models of their vehicles.