Yeah, that works great, and is my favorite. Most people don't have ready access to it, though. Like Phil says.. it can be subtle. I had a persistent mist from Rosie (Rosso Corsa) for a good while. Changed gaskets, lapped the valve cover flat, etc. Finally, using developer and patience, found a literally pin hole in the valve cover casting. It wouldn't leak until the engine was hot enough to thin the oil.