Where is the oil filter located on a 1989 Buick Century?

It's a 4 cylinder and we have looked quite hard but just cannot seem to find where it is located. Yes, we feel foolish. Any more help will be much appreciated. You failed to list which engine. There is a 4 cylinder and a V6. But no matter, I can assure you both engines have an oil filter. If you will crawl under the car and look hard, you will find the filter.