temp drop

I have a 2002 chevy cavalier and a couple of weeks ago after an oil change I noticed that the temp would drop when I went over 70 and would continue to fall until I went below 70.If anyone has any suggestions it would be greatly appreciated..

I do not think your oil change has anything to do with it. The cooling system basically works like this: Once the internal temp of the car reaches a certain degree, the thermostat opens and allows the radiator fluid to pass through the upper radiator hose to be cooled by passing in front of the radiator. Travelling down the road would keep airflow and keep the engine cooler. Some people use an "old trick", never tried it, by putting a piece of cardboard in front of the radiator to restrict the cold air flow.

Cardboard does work. Many Semi-trucks do this with a snap on vinyl cover. Look around, you'll see them as the covers go on the outside.