Whenever I start my deville, on the on-screen dashboard the "Check Oil" light flashes on. I checked the "info" on the dash and my oil level reads 78% and the trans fluid reads 100% What could cause this to come up? How can I clear it?

 

If the check oil light is on you should check the oil level at the dipstick. The 78% indication in the dash refers to the recommended life of the engine oil not the level of the oil. Do not drive the vehicle when it is low on oil. It is good to get in the habit of checking the oil when you fill up so that you can find a leak when it happens and before it causes damage.

Adding oil to the proper level should clear the light.

I recommend changing oil by the odometer reading rather than the dashboard indicator because it is better for the engine. My Seville generally reads 45% to 50% oil life at 5000 miles.