What causes this?

[BG-33P]

Hi,

Just pulled the valve cover off my b16 today and found everything in the head has this 'stained' look to it: (I think it may be called oil coking)



Thats not from my engine but the whole head looks like that (actually a bit worse). I pulled the dip stick out and it looks the same as well.

I recently bought the car, and the car passed a compression test with 200 - 205 in all cylinders when warm and the oil level is correct. On my previous b16 I never experienced anything like this.

I'm going to change the oil as a precaution to some 10-30 fully synthetic oil, but would really like to know what has caused this. The engine sounds fine and runs well but it is rather concerning.

Any help would be great.

Thanks

[1.mile]

"Oil stain", should always look for this when buying a car by opening the oil cap and looking inside.

It indicates that the engine has not been very well taken care off ie. Late oil changes, crappy oil etc etc

Doing an oil flush and put some fresh stuff in there, preferably one with some good cleaning agents may help.

[aaronng]

Caused by the engine oil subjected to extra long service intervals and/or prolonged high temperature. You tend to get this with mineral oil if it is pushed hard and still not changed every 6 months.

[MEN15S]

its caused by not changing the oil for a very long time, it would indicate that the last owners never done regular servicing its nothing to be worried about if you had comp test and you are going to take care of it, just run a oil flush when you change your oil the next few times by the looks of it and what you said about comp test you shouldn't have anything to worry about

[BG-33P]

Thanks guys,

Yeah it passed the comp test fine. I've recently done a radiator swap and an oil change and there was no milkyness evident so I should be good.

Whats the process for oil flushing? Is it just changing your oil really frequently a few times or is it something different you run through the engine?

I've switched the engine to castrol 10-30 fully synthetic. In my previous b16 I was using castrol sport 5-30 but opted for the 10-30 for this one. Opinions?