Not speaking from experience but from looking at informative YouTube videos of so-called experts, it is best done by removing the oil pan and looking at the base of each cylinder when the pistons are at the top. They also say it is most likely on cylinders 5 and 6.

 

Do you have pictures of what scoring looks like?

Where you using your 991.1 as a daily with short commutes and also in the winter? There is a chap who had bore scoring on a 997.2 TT - car was dailyed even in winter with no oil change in winter (but car had its annual oil change). Engine was eventually replaced...

 

If oil consumption is low, would it be safe to say that the unit is fine bore-scoring-wise? Or the symptoms vary?

 

I was 3rd owner, so not sure about its first 29k/6 years, but it is just a well-maintained weekender for me. I doubt it was anything I did.

Yea ill upload a couple pics

 

There is a 4-Part series by the PCA on YouTube.

 

I'm not an expert on this whatsoever, just halfway decent at following breadcrumbs. I got suspicious after smelling the fuel in the oil on changes, plus seeing it on two samples. I then scoped cylinders when I was doing plugs... The two back cylinders on drivers side were the worst.

If you google 9A1 bore scoring you will see this is a thing, not super common, but is a thing for sure.

Here some good info, the first pic you can see the lines going up to the top of the cylinder.
https://lnengineering.com/products/w...1.html?limit=8

 

Pics


These are top of piston, see those shiny scratch like marks? Not sure what scratched it, air filters were always clean, oil reports never showed any signs of intake contamination






Here’s a couple of cylinder walls, see those long shiny lines that are running up down cylinder. 4 of
the cylinders had none of this.

 

Found the video of Jake Raby going in from the sump side, chek out the 2:50 mark for a clear pic. This is part 1 of a series.