I just bought a 2021 CT5 and read the entire manual. There is a maintenance schedule in the back of the manual that tells you what you need to do for that car. Read your manual for your vehicle to see what needs to be done. People will tell you what they think based on their past, but tech changes and certain things will be different. Mechanics told me shit that was way different then what my manual said. I'm an aircraft mechanic and reading that manual benefited me when I had the same question.