What's the 2002 cadillac deville oil type?

The oil type used on the 2002 Cadillac DeVille is SAE 5W-30. If You happen to live in an area where it gets as low as 0F, then You should use SAE 10W-30. Remember when You are changing Your oil to also change the oil filter. The purpose of engine oil, as You may already know, is to keep the engine lubricated. Not only does it keep it lubricated, but it also cleans, reduces friction, and prevents it from overheating. I recommend checking the oil at least once a week so that You're not driving around with a low amount. Driving with low a low amount of engine oil can damage Your engine and its parts.