Well it depends on the type of car. Hope I helped!
The 1989 Ford Mustang 302 cubic inch engine has an oil capacity of 4 quarts. The engine oil should be changed every 7000 miles or every three months.
Every three months or three thousand miles is recommended.
The manufacturer recommends that you change the oil in your 2003 Ford focus of every 7500 miles, or every three months. Engines with a lot of miles on them should be changed more frequently.
Quarterly.
Quarterly
The oil is at least a quart low. Usually, the bottom of the dipstick is 1.5 quarts. If you feel comfortable add a quart, let the engine sit (off) for about 10 min. Then recheck. Engine oil should be changed, at least, every three months. If it has been longer or over 3000 miles get the oil changed. If it has been three months or less and the oil is this low, get it to a service center. GM vehicles are notorious for blowing engines due to oil or coolant leaks.
Every three months
Every three months is called a quarter. And there are four quarters in a year.
seasonal change
To be on the safe side, you should change your email password every three months. Some email programs are more secure than others. Most of them suggest changing it every three months on average.
Change oil every three months
Furnace humidifier filters should be changed at least every three months so they work efficiently. If not changed they trap dust and particles that can 'pollute' the air you breathe. http://yourfilters.com/