PaulTT

Not possible to have moisture in the catalytic converter. I think he might be referring to the rear exhaust silencer.

Indeed, this issue had been addressed with Gen3, hence signs of oil consumption appear very late (or not at all) and are rather insignificant compared to that of Gen2. However, since the low tension piston rings became a standard, you will find this problem associated with all brands, especially combined with the (crazy) long oil drain intervals recommended by the manufacturer (and followed by most of the owners). Short OCIs, high quality oil, engine flush at least once a few oil changes will keep problems away. A piston soak should solve it.

Engine flush will help as well (repetead few times with short OCIs). Berryman product seems to be the best choice for piston soak, but not easy to source within Europe (tried to find it with 0 success). Another great product (and easier to source) is Amsoil Power Foam (fill the cylinders directly through the spark plugs holes and leave it for 2-3 hours).

The plug shows that a lot of oil is burned. Most probably the oil rings are clogged and stuck.

That's the Octavia II, with the 1.8TSI EA888 GEN2 not the Octavia 3 1.8TSI EA888 GEN3. Different engines, 3rd generation being revised and significantly updated. @scout18 - Yes, it does have the secondary set of injectors (has both port and direct injection).

If you can do the test, go for it! It should tell which of the cylinders are more affected.

That'a different generation of the 1.8 TSI (GENII, well known for the oil consumption) while mlimseth has the GENIII. @mlimseth - The following might help with this issue: 1. Check the PCV valve and replace if required; 2. Before changing the oil, use and engine flush (e.g. BG EPR, Amsoil engine flush, Liqui Moly engine flush). Do this for several short interval oil changes and see if there are improvements; 3. Try to do a piston soak (you'll find a lot of information about this with a simple search). Points 2 and 3 will help if you have stuck piston rings (which I suspect you do). Do not use a high viscosity oil, you'll do more harm than good with a low quality 10W40.

He mentioned "1.8L turbo 4cyl" therefore it must be the 1.8TSI EA888 3rd GEN / Mk3 Octavia.

I think his engine should be EA888 3rd Generation, Euro 6 emissions 1.8TSI, that has none of the above issues (and doesn't have an EGR valve)...

Had one fitted recently on a 1.8TSI (2016) (same reason, to get rid of the wheel hop and chose the red one for as little as possible added NVH). Vibrations (+ harshness and some noise) have been a real nightmare from day 1 and things did not improve (not even a little bit) in one month and about 2.000 km. With a/c or windscreen heating on it was literally unbearable. Took it off and the car feels like a Bentley now... 🤣

The 1.8TSI has a timing chain and the spark plugs should be changed every 90k km (56k miles). The engine is indeed great, there's no doubt about this (I'm a happy owner of one 2016 Octavia III 1.8 TSI). From personal experience, I can confirm that the EFB battery (mine was MOLL) is prone to "sudden death". Mine just died (literally) overnight, with no previous signs or warnings, after just 5 years of almost ideal usage pattern (replaced it with a VARTA AGM a few months ago).