Does anyone know what is this (beige color)?
It is oil filler cap.
I purchased this vehicle few weeks ago. Previous owner changed engine oil 3 years ago using Mobil 1 Fomular M 5W-40 and drove only 3K miles after that.

That is from moisture in the engine, most likely from sitting so long or short trips and not getting the oil up to temp.

Thanks for coment!
Is it harmful?
I found this yesterday and changed oil.

After little researching, I realized this also could be happened when head gasket blown.
But when I drained all oil yesterday, I did not see any of milky oil. I hope it is not the case gasket issue.
Thanks, 'Shifter' for your info again!