Is it OK to add oil when engine is hot?
Yes, you can put oil in a hot engine.
Whether your engine has been running for an hour or only a few minutes, adding cold oil to a hot engine will not harm it. This is, however, only recommended when you are simply topping off your oil rather than changing it or checking the oil level.
Should I let my car cool down before adding oil?
Your engine should be cool, and you should wait at least 20 minutes to give the oil time to drain fully back into the sump. 4. Check the level again using the dipstick, and keep adding oil in small amounts until you are happy with the level.