Now watch as the engine runs. Check for smoke coming out of the oil fill hole.

The video here shows little to no smoke; this indicates low blow-by.

Wisping or small puffs of smoke indicate normal blow-by for a higher mileage engine.

If it's puffing like a steam locamotive, you'll want to investigate further!

Then, as the video shows, set the oil cap back on without tightening it.

If it just wiggles a bit, you're in pretty good shape.

If it dances around, and hops up and down, there's some blow-by but probably nothing to get excited about.

If it is hard to keep it on, for risk of taking off a finger, there's an issue!!