Jacking up the car is not strictly necessary to change the oil on all E30s. I have lowered my car, so a drain pan will not fit under it as it sits on the ground. When my car was at stock ride height, I was able to change the oil without jacking it up by using a low profile drain pan.

Before lifting the car with a jack, be sure the car is in first gear for manual transmission cars or in park for automatic transmission cars.

Additionally, be sure to firmly apply the emergency brake.

You may also wish to put chocks behind the rear tires to keep the car from rolling. My emergency brake system is brand new, so I don't usually use chocks. If you are unsure, either use your factory wheel chock or put a brick/4x4 behind one of the rear tires.