Hmm .... well, obviously the oil has to be able to get into the combustion space above the pistons somehow, and there's a limited number of ways it can do that.
1. It sneaks past the piston rings - compression and oil control rings.
2. It leaks down the valve stems due to worn valve seals.
3. It comes in as a mist of fine oil droplets in the combustion air.
If 2, then it will tend to smoke on start up, but will clear with time.
If 1, then high rpm will make the smoke worse as more oil is introduced due to the higher number of piston strokes per minute.
If 3, then there would be signs of oil misting in the inlet tract downstream of the pipe from the PCV.
The PCV is quite cheap to replace, even for a genuine Honda one, so it might be an option?
On the Porsche Boxster flat 6 engine, there is a similar device known as an "air / oil separator", which is connected with hoses to the sump and the inlet manifold. Inside it is a diaphragm that modulates the vacuum in the sump, and when it fails, the sump vacuum defaults to that of the manifold and oil droplets are then sucked into the manifold leading to plumes of blue smoke that doesn't stop with time.
The Jazz PCV does look very small in comparison with the Porsche one though .....
A compression test on the 4 cylinders might be revealing?
Having said all that, my neighbours Toyota used to drink oil with no sign of any leaks and I never saw any smoke at all coming out of the exhaust, so I have no idea where it was going.
Also, the oil level on our 2003 125,000 mile Jazz dropped a little for the first time ever, and I'm wondering if that was related to a period of very high rpm making sure I didn't stall in some deepish water the other day ....
