Several addtional things to look for:
1. Crankcase oil that gets dirty very quickly.
2. Remove your oil filler cap with the engine running at low rpm and put your hand over the filler hole. You may be able to feel the puff-puff-puff at very low rpm.
3. When the engine is hot, remove the oil filler and put a sheet of paper or light cardboard near the filler. It will move with air puffing out. This may be hard to do/see if your fan is also close-by.
4. With severe blowby, you'll have oil and smoke coming out of any crankcase vent opening.
5. Do a compression check. All or some cylinders will show low compression. Spray some light oil in the cylinder at the sparkplug hole if it's a gas engine. You should see a big jump in compression with oil in the cylinder.