Spark plug oil on threads

[PIC_3G3]

I have a 2016 Silverado 1500 with the 5.3L engine with about 87k miles on it. Pulled a few plugs today to check the condition as I know the manual says they need done soon and notice the first one I pulled (cylinder 1 I believe. Driver side front) had oil on the threads. I pulled the one right behind it and it didn’t appear wet at all. Any ideas what the likely cause is? There are no codes and the engine seems to be running fine. I simply wanted to check the condition of the plugs to gauge whether replacing soon was necessary. 

Edited May 12, 2025 by PIC_3G3

[rav3]

Which engine is this?

From my shade tree mechanic work, your plug tip looks good. A little wear, but not bad. I'd check the gap to see how much wear is there. I would guess that your oil is coming from the outside & not from inside. On the 5.3, the oil cap is close to that plug. Have you spilled any oil while adding?

Also, check your valve cover gasket for any oil leak on that side.

Edited May 12, 2025 by rav3

[PIC_3G3]

21 minutes ago, rav3 said:

Which engine is this?

From my shade tree mechanic work, your plug tip looks good. A little wear, but not bad. I'd check the gap to see how much wear is there. I would guess that your oil is coming from the outside & not from inside. On the 5.3, the oil cap is close to that plug. Have you spilled any oil while adding?

Also, check your valve cover gasket for any oil leak on that side.

Thanks for your input. It’s the 5.3. No oil has been spilled that I am aware of and the engine and plug wires and boots look clean so doesn’t seem like any oil has spilled at least not recently. I’ll look into the gasket. 

[CamGTP]

DoD cylinder tend to have oil on the threads. Those being cylinders 1, 4, 6 and 7.

[PIC_3G3]

41 minutes ago, CamGTP said:

DoD cylinder tend to have oil on the threads. Those being cylinders 1, 4, 6 and 7.

Ok so this is normal and nothing to worry about?

[CamGTP]

Yeah it's usually pretty normal to see. Oil gets past the piston rings and possibly the valve seals on the cylinders that shut off on the freeway. Some engines will burn a little more oil than others but seeing a little oil on the threads I find pretty normal.

[PIC_3G3]

1 minute ago, CamGTP said:

Yeah it's usually pretty normal to see. Oil gets past the piston rings and possibly the valve seals on the cylinders that shut off on the freeway. Some engines will burn a little more oil than others but seeing a little oil on the threads I find pretty normal.

Thank you very much!