Back in the day, it wasn't uncommon to have to change a car's oil every 3,000 to 5,000 miles. But technology and design have evolved, and you may be surprised to learn that you need not change your motor oil as frequently as you think. The simplest way to find out is to visit checkyournumber. org and enter the year, make and model of your car. It will tell you the exact manufacturer recommended oi…