It feels like a lottery what reading you get on the oil stick. I changed oil, ran the engine, then let it cool for a minute or two - no reading. So I topped with some extra oil, ran the engine again, let it cool a bit. Now reading was at the bottom of the stick. So I topped again, ran engine, let it cool a bit. Now I have no reading again. I don't want to just keep filling because that's what I did yesterday and then I did not get a reading until very suddenly after about 2.9L, then I got a reading which was way over the maximum level.

How does this actually work? When and how can you be sure the reading is correct?

I mean how difficult can it actually be???????