Adding Sea Foam to a full crankcase [SOLVED] Asked by Cletus A. In Ohio Can I add Sea Foam even if my engine crankcase is full of oil?
As long as it’s not overfilled, you can add the Sea Foam without draining any oil. Add 1 ounce of Sea Foam per quart of oil. A crankcase has plenty of capacity for the Sea Foam, so no worries.