Spark plug condition and what it says about the engine's overall health?

[GolfVFSI]

Hi everyone,

Replaced the spark plugs on a 2.0L FSI engine with 150,000km.
Apparently we can determine the overall health of an engine by checking spark plugs

For example I read online that in general, a light tan/gray color tells you that the spark plug is operating at optimum temperature and that the engine is in good condition. Dark coloring, such as heavy black wet or dry deposits, can indicate an overly rich condition.

The old spark plug I removed looked like this. What do you reckon?



Also I noticed on the other end of the body a gold coloring as illustrated below. Any idea what it could be/what it means?



Also, here's a look at inside. Looks clean besides a bit of what looks like oil deposit but I've seen worse. (The ignition coil where in good condition).



However, cylinder 4 had some sort of deposit on the head cylinder, where the spark plug sits. When I started unscrewing the old spark plug, it felt like there was "sand" between the spark plug and head cylinder. Upon inspecting the head cylinder I could see some debris down there.



Any idea what it could be and could it be dangerous for the engine? I didn't have anything to suck it out unfortunately.

Thanks for any insights you may have

[h100vw]

Those plugs have likely never been changed.

I'd personally not be worried about whats on them as it will run so much better with new ones. Have a look at the new ones after they have done a 100kms to get a better idea of how they are.

[GolfVFSI]

Oh yeah I know, it's not a I have an issue type of thread, car runs well and like you said with the new spark plugs it will be even better.
It's more for insights/knowledge purposes. I'm by no means an expert in mechanic but I'm learning.

It's just that I read a few articles online that says that you can determine the overall health of an engine by checking the condition of a spark plug and I thought it was interesting.

For example here Reading Spark Plugs Color | Champion Auto Parts
Thew show how a "normal"used spark plug should look like


But mines are dark/black at the end.

Black, dry soot on the electrodes and insulator tip indicates a carbon-fouled plug. This can be caused by a dirty air filter, excessive driving at low speeds, too rich of a fuel/air mixture or idling your vehicle for too long.

Or a black tip could indicate oil deposit which could mean that oil is leaking into the cylinder and if that's the case I guess it's something good to be aware of.

If anyone else has experience "reading" spark plugs please let me know, I'm interested to hear your thoughts.

Thanks