[Thethinkingbear]

My 19 G20 has ~ 40k miles, recently I noticed lower mpg and slight struggle/vibration when moving from a traffic stop in Comfort mode. It's like putting a manual car in 2nd gear below 10mph, but not to the same extent. No such feeling in Sport mode. There was no misfire nor any warning light on dash. I thought maybe the engine air intake filter got dirty (actually not) and replaced it anyway. Didn't seem to improve much. I didn't think about spark plugs since my impression is they last at least 60k miles.

Recently it's due for oil change, and dealer recommended spark plug replacement based on mileage. I decided to do it myself, knowing it's a simple job and I can do it at 10% of the cost. Everything went well, except that I found the 2nd spark plug chamber has some brown colored oil (pictures attached). Not sure if it's engine oil or buildup impurities from gasoline. The oil seems to be thin and mostly on the outside of the plug, not much on the thread and tip; there is some oil on the rubber tip of the coil, the metal spring inside is not contaminated.

View post on imgur.com

I just wiped clean the chamber and tip of the coil and put the new plug in. Everything works well. The struggle/vibration seems to be improved. MPG needs to seen after I drive for longer.

Now, regarding the oil in 2nd plug chamber, some articles online suggest it may be spill during a sloppy oil change job. And it is indeed the one that is closest to the engine oil refill cap. But I don't see any oil in the surrounding area. I'm the original owner and oil change was always done at dealership. Should I be concerned about internal leakage and how long should I drive the car before pulling out the coil and check again to see if there is any new oil?

Thanks!

[hrf]

Could be your valve gasket leaking. Not a big deal to replace, but I think it is sealant now, so need to clean old sealant and apply new one.

[HFW003]

If it’s not on the thread or electrode I would bet it’s just from a previous spill.

[jhm5]

Looks like it leaked down from the valve cover gasket... my guess.

[Thethinkingbear]

Originally Posted by hrf

Could be your valve gasket leaking. Not a big deal to replace, but I think it is sealant now, so need to clean old sealant and apply new one.

Sorry, what do you mean by "sealant"? which part is it for?

[Thethinkingbear]

Originally Posted by jhm5

Looks like it leaked down from the valve cover gasket... my guess.

Thanks.
down or up? I never knew about the "valve cover", did some search and looks like the gasket seal is where the plug meets the engine body, the deep hole that the plug sits in is just an indentation on the valve cover body as a whole piece. So if it's the gasket leaking, the engine oil goes up from the engine up through the leaky gasket to the spark plug hole. Is my understanding correct?

If I check again after driving a few weak and see no oil, ok to assume the gasket is not leaking?

[hrf]

Originally Posted by Thethinkingbear

Sorry, what do you mean by "sealant"? which part is it for?

BMW does not use gasket on valve covers anymore. It is a sealant which you can buy as BMW part or permeatex.

https://www.fcpeuro.com/products/ult...CABEgKoqPD_BwE

https://www.turnermotorsport.com/p-2...yABEgLB-PD_BwE

[Thethinkingbear]

Originally Posted by hrf

BMW does not use gasket on valve covers anymore. It is a sealant which you can buy as BMW part or permeatex.

https://www.fcpeuro.com/products/ult...CABEgKoqPD_BwE

https://www.turnermotorsport.com/p-2...yABEgLB-PD_BwE

Wow, thanks! This is new to me.
It seems FCP Euro still sells the "OEM" gasket that claims to fit G20:
https://www.fcpeuro.com/products/bmw...76-450#fitment

Maybe both would work?

[hrf]

Both should work. Important is to clean both cover and head junction areas really well before applying sealant. I think there sre plenty DIY videos on rhis on you tube.

[SenatorPickle]

This is one of the earliest valve cover "gaskets" (seal) that I have heard of failing. This was also my initial guess reading this. Its been one of the BMW theme songs throughout recent decades across multiple engine designs. They all go someday; I was actually searching for forum myself to gain a sense for averages on when these fail on the G20 platform (regardless of B46/B58). My experience in the E90 is upwards of 100K between failure points, but there are many factors (climate, maintenance, heat-cycling, manufacturing tolerances of your specific block/valve cover mating surface - to name a few).

Pro tip on the G20 that I'm finding out is definitely to replace the valve cover as well during the process. Why? The PCV (another inevitable failure point) is integral to the valve cover now...... sigh.

[SenatorPickle]

Thethinkingbear, If you happen to see this, I am curious as-to your oil change intervals?

In the event a motor experiences long service internals beyond the BMW recommended interval, that could also be a factor in premature degradation of this seal.

[bavarianride]

Originally Posted by hrf

BMW does not use gasket on valve covers anymore. It is a sealant which you can buy as BMW part or permeatex.

The G20 appears to still have gasket part#11128638247(for B46) and part#11129894803(for B58).

[Thethinkingbear]

Originally Posted by SenatorPickle

Thethinkingbear, If you happen to see this, I am curious as-to your oil change intervals?

In the event a motor experiences long service internals beyond the BMW recommended interval, that could also be a factor in premature degradation of this seal.

I go by the recommended oil change interval as shown on the dash board, usually 9-10k miles or 11-12 months whichever came first.

Driving in comfort mode most of the time. Nothing crazy.

Note, I haven't confirmed whether this is a external leak from a previous oil change or actual leaky gasket.

[bavarianride]

Originally Posted by Thethinkingbear

Note, I haven't confirmed whether this is a external leak from a previous oil change or actual leaky gasket.

if there is no new leaked oil after the old one is cleaned up, then it is likely not an active leak that can worsen with time.